The Audi A4 is one of the better cars in a crowd of smaller sport-luxury sedans that, dollar-for-dollar, offers some of the best, most appealing vehicles in the world.

To be sure, Audi's A4/S4 line is more than sedans. For 2007, all-new convertibles augment the existing four-door models and wagons. Also new is the ultra-high performance (and at $66,000, expensive), 420-hp RS4. From the enthusiast driver's perspective, it's one of the best sedans ever.

The A4 line is complex, with 21 variants. The key is thinking according to priorities: body style, engine size, front- or all-wheel drive, transmission type. All are nicely balanced, enjoyable automobiles.

The A4 2.0T, still priced well below $30,000, is fun to drive. Its turbocharged, 200-hp four-cylinder is one of the better small engines going, with satisfying response and spry acceleration, particularly with the standard six-speed manual transmission. It corners like a sports sedan, and high-quality construction is evident inside and out. Audi's optional quattro all-wheel drive system can help keep the driver on the road regardless of the conditions or situation, and buyers don't have to choose a big engine or special model to get it.

Going up the line, there's a smooth V6 and two powerful V8s. Those who frequently carry gear, dogs or cargo will appreciate the A4 Avant, which offers the extra space of a wagon while maintaining the A4's sporty driving character. The new convertibles are stylish, sexy and reasonably practical, and they don't have to cost an arm and a leg. The S4 models will appeal to enthusiast drivers who crave their lusty power and sporty handling, for a lot less cash than the RS4.

Every A4 should appeal to techies. State-of-the-art engines feature direct fuel injection: the cleanest, most efficient means yet devised to blend gasoline and air in an engine's cylinders. Transmission choices include a six-speed automatic with Tiptronic manual-shift feature and an efficient continuously variable automatic (CVT) that delivers truly seamless shifting. Sophisticated suspension technology is augmented with electronic stability control, which can help the driver avoid a crash. The A4 is stuffed with safety features and offers rear side-impact airbags, while most cars in its class don't.

Unlike other tech-heavy cars, the gizmos blend nicely in the A4, enhancing comfort, convenience and safety, and improving the driving experience.

The A4 can be pricey and it's relatively small. On the other hand, you'll have to look long and hard to find a car that blends driving satisfaction, safety, convenience, practicality, great finish and reasonable ownership cost as well as the A4.

The 2007 Audi A4/S4 line offers a potentially confusing array of sedans, wagons and convertibles with four-cylinder, V6 or V8 engines, front- or all-wheel drive and a choice of six-speed manual, conventional six-speed automatic or continuously variable (CVT) automatic transmissions. The line includes 21 separate model variants.

Consider the possibilities in this order: body style, engine, drive system and transmission. With the standard A4 sedans, think of Audi's popular quattro all-wheel drive system ($2,100 or $2,200, depending on the model) as an option. One of the two types of automatic transmissions ($1,200) can be considered as an option on most variants.

The A4 2.0T sedan ($28,240) is the least expensive model, powered by 200-hp, 2.0-liter turbocharged four-cylinder engine. The 2.0T Avant ($31,340) and other wagons come only with quattro, which is included in the price.

The standard upholstery is cloth, but the A4 2.0Ts come with lots of features, including dual-zone automatic climate control with cabin filtration, cruise control, tilt and telescoping steering wheel, power driver's seat, auto-on running lights, a 10-speaker stereo with six-CD changer and 16-inch aluminum wheels.

The A4 2.0Ts offer two option packages. The Premium Package ($1,900) includes a power glass sunroof and 17-inch wheels. The Convenience Package ($1,900) adds driver's seat position memory, Homelink remote transmitter, rain and light sensors, auto-dimming inside mirror with compass, auto-dimming and power folding outside mirrors and Bi-Xenon headlights with adaptive front lighting.

The A4 3.2 sedan ($35,540) comes standard with the CVT automatic, while the quattro models, including the 3.2 Avant ($37,440) offer the manual. Besides a 255-hp V6, the A4 3.2s add leather upholstery, sunroof and 17-inch wheels.

Additional option groupings for the A4 3.2 include a Cold Weather Package ($1,000) with heated seats and a ski sack, and Audi's S-line Sport Package ($2,750), which adds 18-inch wheels with performance or all-season tires, sport suspension, brushed aluminum trim and S-line styling tweaks.

Next up are the sport-tuned S4 sedan ($47,500) and Avant ($48,500), which feature a 340-hp 4.2-liter V8 and standard quattro. The S4s offer the DTM Appearance Package ($1,500), which is named for Germany's equivalent to NASCAR racing and includes carbon-fiber spoilers.

The A4 Cabriolet, or convertible, has only four seat belts, and is available in five models that roughly correspond to the sedans and wagons: 2.0T CVT ($39,100); 2.0T quattro with conventional automatic ($41,200); 3.2 quattro with automatic ($46,950); S4 manual ($55,700); and S4 automatic ($56,900).

The are lots of stand-alone options for all A4 and S4 models, including a navigation system ($2,100), a Bose stereo upgrade ($1,000) with XM satellite radio receiver, Parktronic distance warning ($350), special wood trim packages ($400) and headlight washers ($150).

The RS4 ($66,000) sits atop the entire lineup. This is a high-performance sedan of the first order, with a 420-hp 4.2-liter V8, manual transmission only and a special quattro system that biases power delivery to the rear wheels. It also includes most of the comfort and convenience features offered across the line.

Safety features that come standard include front-seat front and side-impact airbags, curtains-style head-protection airbags front and rear, and advanced, full-feature electronic stability and anti-lock braking systems (ABS). Rear-seat side airbags ($350) and a tire pressure monitor ($250) are optional.

The Audi A4 looks like a premium-grade car. It's classy and assertive, just short of overtly aggressive, with a tidy, well-planted stance that oozes presence. That presence is strong enough to disguise the A4's dimensions.

This is a relatively small car: considerably smaller than competitors like the Cadillac CTS or Infiniti G35, and very close in most measures to the compact Honda Civic.

The eye immediately settles on the A4's big, tall grille, of which opinions vary. The only consensus seems to be that it's different, and it immediately identifies the A4 as an Audi.

The headlights give the front-end an assertive look, with lenses that angle upward as they wrap around the fenders. Laterally split intakes below the body-colored bumper and outboard of the grille do double duty, housing fog lamps and channeling air toward the front disc brakes. A modest hood swell, which designers call a power bulge, carries the grille's vertical outlines back to the roof pillars. On the ultra-high performance RS4, the hood and fenders are fabricated from aluminum to reduce weight.

The A4's profile shows a sharply creased shoulder line running the length of the car, from the trailing corner of the headlights to the leading edge of the tail lights. The side windows are nicely proportioned to the body mass, atop a relatively high beltline. A bump strip breaks up the expanse of the lower door panels. The painted door handles look great, but they are hard to grab and can snap away from your fingers when you're in a hurry.

The A4 Cabriolets look good with the convertible top up and much better with it down, which is probably the way it should be. The fully automatic, electro-hydraulic roof will open or close at speeds up to 19 mph. That's handy if a rain squall sneaks up while profiling through town. The soft top is thickly insulated, with a glass rear window and defroster, so it shouldn't be too big a detriment in cold climates.

The premium-grade look outside the Audi A4 carries through inside, thanks to clean, elegant design, generally rich-looking materials and good finish work. Colors combinations tend to be muted, and a choice of wood trims or aluminum inserts complement the leather, cloth and plastics.

The standard A4 seats are well bolstered, with plenty of lumbar support. We found them comfortable. The sports seats in S and RS models have big side bolsters that are harder to slide over, but the payback is Velcro-like grip on a driver's backside and torso. The standard cloth upholstery feels durable and provides a bit of grip itself. The optional leather surfaces are elegantly stitched and fit our posteriors well. The seats, mirrors, steering column and other features adjust in every conceivable direction, helping drivers find a comfortable seating position.

Interior space, however, is not one of the A4's strengths, even compared to some sedans with similar exterior dimensions. To be sure, there is more than adequate space for average-sized adults to adjust, move and stretch in front, without pangs of claustrophobia. But the A4 may not be a car for the truly full-figured, or people who rise taller than six feet, two inches. On a regular basis, the smaller space in the back seat is best reserved for children and pre-teens.

All of the A4's controls are focused on the driver; with few exceptions, they're ergonomically configured and intuitively located. The steering wheel hub repeats the grille's trapezoidal outline. A minimalist set of secondary controls on the wheel spokes manages audio and other functions. Column-mounted stalks operate the usual array of features and are clearly marked, except for the rear wiper/washer switch on the Avant, which is controlled by the right-hand lever. We like Audi's lane-change signal feature, which delivers three turn-signal blinks with a tap on the lever. It works much better than some other manufacturers' efforts to re-invent the turn signal, most particularly BMW's.

The A4's gauges are shaded by a hooded panel and easily viewed through the top half of the steering wheel, regardless of how the wheel is adjusted. The TFT information display, reporting such data as radio frequency, trip mileage and service interval warning, separates the tachometer and speedometer, with fuel and coolant gauges tucked down in the corners.

Knobs and buttons for the audio and climate controls are clustered in the center stack, all easily deciphered and within easy reach. The climate system is easy to operate, but the air conditioning struggled to keep up on a 95-degree day driving through the desert. It was about then that we noticed that, at certain angles, the sun reflected up off of the silver trim surrounding the shifter on an A4 2.0T sedan.

When the navigation system is ordered, the stereo panel gives way to the map display, which then doubles as stereo controls. The display is one of the best available, and system controls are readily understood. It's easy to orient the cursor and shift the map scale, while on-screen telltales steal very little real estate from the map. The map offers both a flat, two-dimensional and a bird's-eye perspective, the latter with a distant horizon visible across top of the screen.

The premium stereo has MP3 capability and a pair of slots for Secure Digital memory cards. Unfortunately, only volume and pre-set radio stations can be changed without first pressing Accept on the opening menu every time the car is started. We find it annoying to sign the electronic equivalent of a liability waiver just to turn on the radio. Also, the stereo is on all the time the navigational system is active, and it's annoying. You don't turn it off, you just turn it down.

There are other minor annoyances with the A4. We wish the beep confirming the remote lock would sound more promptly, as we constantly found ourselves pausing for a moment to be sure the doors had in fact locked. And while we're strong believers in seat belts, we found the warning chime annoying because it would urgently sound immediately after starting the car, before we started driving. In other words, you're not allowed to just sit there with the engine running without buckling up.

As for unusual positive impressions, we like the one-piece wiper blades for their sleek looks, slicker aerodynamics and solid seating against the glass at autobahn speeds. And we were thankful for the red Stop button on the driver's memory settings panel whenever we pressed the wrong memory setting button.

There's a lot more useful storage spots in the A4 than there were in Audis or recent past. It starts with an impressively big glove box, though the box gives up space to the CD changer if the navigation system is ordered. There's a neat drawer the size of a credit card above the in-dash CD changer. The front doors have fixed map pockets, and the front seatbacks have net pouches to hold magazines, snacks and other sundries. A power point in the center console bin augments the cigar lighter in the front ashtray. A flip-down armrest in the rear seat contains two cup holders.

The A4's fold-down, height-adjustable front center armrest can align with the driver door armrest, encouraging a restful, upright driver posture, but it also can interfere with operating the handbrake. Pulling the brake lever requires contorting the wrist or raising the armrest. Some of us loved the center armrest; others found it a pain and immediately raised it upon getting in the car.

With 13.4 cubic feet of trunk space, the A4 sedan falls slightly above the mean in this class. Moreover, the space in the trunk is made as useful as possible. The trunk lid flips out of the way for easy access. There are cubbies in the trunk side panels that take advantage of space around the wheel wells, and several tie-down points.

The Avant features a two-way cargo cover that includes a pull-up, vertical net to restrain stacked objects, or maybe a dog, behind the rear seat. It could be important in an accident. Pull-down grips inside the liftgate spare your hands from any road grime accumulated on the outside.

The A4 Cabriolet gives up a seat-belt (and therefore a seat) in back, but if you were the person relegated to middle-rear in the sedan, you might not consider that any great loss. The convertible also gives up some trunk space to make room for the top mechanism, reducing maximum capacity to 10.2 cubic feet. There's still plenty of room for luggage.

The standard soft top is well insulated against cold air, and to a lesser extent, noise. Audi also offers an acoustic roof, which uses more expensive fabrics with a greater material density. The company claims this top reduces interior noise levels to those in the A4 sedan, even at highway speeds.

The Audi A4 offers good handling and response, making it a lot of fun on winding roads. It's extremely stable at high speeds, as one might expect from a bigger, heavier car. Its engines range from spry and economical to Holy Cow! with gas guzzler tax.

The A4 is Audi's counterpoint to the BMW 3 Series, and we'd venture that each is the other's most obvious, direct competitor in the market place. The A4 is clearly competitive with the 3 in the quantifiable, objective measures. Much of the subjective and visceral is present and accountable, too. Even where it follows a different track, it doesn't stray too far. But in one measure, it's far ahead. Audi's quattro all-wheel drive system is almost legendary, and much better sorted than the all-wheel-drive systems offered in the BMW 3 Series and Mercedes-Benz C-Class. Meanwhile, the Acura TL and many other cars that compete in the sporty, near-luxury class only come with front-wheel drive.

The A4 lacks the quiet, almost Zen-like solitude afforded by some of its competitors, but those who appreciate its lively traits will find it more than quiet and smooth enough. Wind and road noise are nicely filtered in the sedan, less so in the Avant, where the large cargo space amplifies the hisses and rumbles. The same large volume of air works well with the stereo, however, giving the bass tones a nice, deep resonance in the Avant.

The 2.0T suffers from turbo lag, a trait that's amplified when paired with the Tiptronic automatic that comes with quattro. The Multitronic CVT (continuously variable transmission) with the four-cylinder and front-wheel drive is a competent package, but it's a combination that doesn't deliver what we look for in an A4. The A4 2.0T's four-cylinder engine works best with the six-speed manual gearbox and that's the combination we'd order here, though we wish the shift throws on the manual were a little shorter.

With the 2.0T turbocharged engine, there's not a lot of power down at the very bottom of the rev range. The manual allows the operator to keep the engine running where the torque comes in greater quantity. Yet even with the manual, the turbo is not great for squirting at a moment's notice, so passing a train of cars on a two-lane road can be a challenge. It's fantastic for winding roads, however, and we had a blast with it on a winding hill climb out of California's Carmel Valley.

The 2.0T does very well on the highway, feeling comfortable cruising at high speeds all day. We did this and got 27 mpg. An A4 2.0T Quattro is EPA City/Highway-rated to get 22/31 mpg.

The 3.2-liter V6 is a much better choice when ordering an automatic transmission. The V6 is smoother and more refined than the 2.0T. With the V6, the six-speed Tiptronic automatic is almost as responsive as the six-speed manual, and by far more accommodating in day-to-day traffic. We prefer to put it in Drive and go, and we suspect most people will rarely, if ever use the Tiptronic manual shift feature.

Those who do will find the Tiptronic falls a bit short in the manumatic game, mostly because it will not allow full manual control of the shifts. An algorithm in the powertrain management computer shifts up a gear to put the engine at the optimum point in the torque curve, and a button beneath the gas pedal shifts down a gear when mashed, as when passing or accelerating up a grade. This is an impressive application of computerization, but it mocks the Tiptronic's promise of a manual-override automatic. In practice, the downshift is occasionally helpful, but the upshift is disconcerting when it occurs in the middle of a corner.

All the A4 models offer crisp steering response with comforting directional stability. All feel planted and confident at high speed. There's less pogo over undulating pavement on fast and narrow winding roads than in other cars. Quick left-right-left transitions are handled with finesse. The same goes for the Avant wagon. The V6 models, which are 150 pounds heavier, feel less agile and slower in response to driver inputs than the 2.0T models. Ride and handling with the base suspension is firm, but not stiff. The optional sport suspension tends more toward stiff, almost harsh. We prefer it, but think most buyers will be happier with the standard suspension.

The brakes offer impressive stopping power with no fade. Smooth stops can be a challenge, however, almost as if all the electronic systems are confusing each other. The brake pads seem to continue pressing against the discs even as the pressure on the pedal is eased. This undercuts the A4's ability as a commuter car in stop-and-go traffic.

The S4 delivers lusty performance from its sweet-sounding V8. It works well with the manual, which is surprisingly easy to shift, considering the amount of power it has to control. The clutch pedal is not overly heavy and the shifter is so easy the clutch hardly seems necessary at times. We drove an S4 Cabriolet and an S4 Avant and found both of them to be delightful cars. It's hard to imagine anyone needing more power. The engine is smooth and tractable at low rpm, though the driver always has a sense of incredible power under foot. The ride quality is firm but tolerable.

The RS4 sedan cranks everything up a few notches, even compared to the V8-powered, sport-tuned S4 models. And at its price, it should. Beyond a 25 percent horsepower boost and weight-reduction measures, its quattro all-wheel drive system is tuned for the track. The default level of power delivery is biased more toward the rear wheels, so the RS4 behaves more like a rear-drive car.

As such, it's one of the best balanced, most drivable performance cars we've sampled, meaning it's not overly inclined to understeer (trying to push straight in front as the driver turns) or oversteer (getting loose in back). It also lets the driver adjust its trajectory by using the gas pedal as well as the steering.

Even in the RS4, there's some level of understeer, which is the default characteristic engineers prefer for real-world safety. Yet in rapid, hard, left or right direction changes, the RS4 is amazingly controllable and requires very small steering input to turn. A driver can actually get the rear-end to slide out with the gas pedal, turning the car more quickly, and then tuck it right back in when the throttle is lightened.

The 420-hp V8 is sweet, generating an impressive 100 horsepower per liter of displacement without a turbocharger. There's a steady flow of torque at any speed in any gear, and a visceral, tingling high-rpm rush that will remind every car enthusiast what he or she loves about driving. In short, from the enthusiast driver's perspective, the RS4 is one of the most entertaining and exhilarating sedans we've driven in years.

The Audi A4 is fun and spirited in any of its 21 variations. It delivers plenty of power, respectable gas mileage for its class, state-of-the-art sound and, above all, an integration of various systems that give it depth and a high level of driving satisfaction. Interior space is tighter than in many competitors, but Audi's quattro all-wheel drive system remains the benchmark. Prices range from the very-high $20,000 range to just past $70,000, when loaded with options. If you plan to look at entry-luxury sports sedans, we recommend that the A4 be one of them.

NewCarTestDrive.com correspondent Tom Lankard filed this report from Tucson, Arizona; with Mitch McCullough in Monterey, Greg Brown in Los Angeles, and J.P. Vettraino in Detroit.