A full-size luxury car is to a millionaire's driveway as a designer handbag is to a socialite's arm. While both serve a practical purpose, the appeal of such trappings of wealth goes far beyond functionality. Some well-heeled consumers subscribe to the "louder is better" school of thought -- and for them, there are plenty of luxury sedans that scream prestige like overexposed couture labels dripping with gold hardware and signature plaid. But for those who prefer a more understated aesthetic, the 2009 Audi A8 is a compelling proposition, even if it won't necessarily raise as many eyebrows in the country club parking lot.

As ever, this full-size luxury sedan features an impeccably finished cabin, refined acceleration and polished road manners. Audi's adaptive air suspension handles both freeway cruises and twisty back roads with aplomb, and unlike its main competitors, the A8 features standard all-wheel drive. The Audi's restrained exterior styling is another strong point, we think, striking a sweet balance between muscularity and elegance. Yet the A8 still lags in sales behind its competitors, the BMW 7 Series, Lexus LS 460 and Mercedes-Benz S-Class, and that isn't because it's more expensive. In fact, the 2009 Audi A8 is a couple grand shy of its BMW equivalent and nearly $9,000 less than the Benz.

The A8 probably owes those underwhelming sales numbers to its slight but undeniable lack of cachet compared with its chief German rivals, as well as its inability to compete with the LS 460's sterling reputation for quality. But other than these perceived deficiencies, the A8 is top-notch. It moves out smartly, handles confidently and coddles its occupants with luxury and style. If you're in the market for a full-size luxury sedan and don't mind being a bit unconventional, the A8 is certainly worth a close look.

The 2009 Audi A8 comes in three trims: base, L and L W12. (The "L" stands for long wheelbase, which provides increased rear legroom.) The base and L models come standard with 18-inch alloy wheels, xenon headlights, a sunroof, Audi's Multi Media Interface (MMI) system, a navigation system, cruise control, leather upholstery, 16-way power front seats, heated front and rear seats, dual-zone automatic climate control, a parking system with a rearview camera, keyless ignition/entry, a power trunk opener, power door closers, Bluetooth and a 12-speaker Bose surround-sound audio system with satellite radio, iPod connectivity and a CD changer. The L W12 comes standard with 19-inch alloy wheels and adds four-zone climate control, ventilated/massaging front seats, four-way lumbar adjustment for all passengers, an Alcantara headliner and a wood steering wheel. Most of the L W12's standard features are available on lesser A8s.

Options include 20-inch wheels, a solar-powered venting sunroof, upgraded leather interior trim, a 1,000-watt Bang & Olufsen audio system and a Technology Package that adds adaptive cruise control, a lane departure warning system and a blind-spot warning system. The L W12 can also be outfitted with a personal refrigerator.

Both the base and L models come with a 4.2-liter V8 that makes 350 horsepower and 325 pound-feet of torque. The L W12 model boasts a 6.0-liter 12-cylinder engine that makes 450 hp and 428 lb-ft of torque. Known as the W12, this engine can be thought of as two narrow-angle V6 engines joined at the crankshaft, making it more compact than a conventional V12. Both engines are matched to a six-speed Tiptronic automatic transmission that drives all four wheels through Audi's Quattro AWD system.

With either engine, this is a quick luxury sedan. The base version can hit 60 mph in 6.3 seconds and cover the quarter-mile in 14.2 seconds, while the W12 betters those stats by about a half second in each case. Fuel economy for the base and L models is 16 mpg city/23 mpg highway and 18 mpg combined. The L W12 achieves 13/19/15 mpg.

Standard on all 2009 Audi A8s are antilock brakes, stability and traction control, full-length side curtain airbags, front- and rear-seat side airbags and active front headrests.

Whether taking off from a stoplight or jetting up to cruising speed on the freeway, any version of the 2009 Audi A8 always puts a solid rush of power on tap. Moreover, the powerful and easily modulated brakes have no problem reining in this luxury liner. While the air suspension works just fine in automatic mode, the "Dynamic" setting tightens up body control considerably, making the A8 feel more like a sport sedan than a large flagship luxury car.

The interior of the A8 provides first-class comfort, especially in the L version, which boasts a limolike 42 inches of rear legroom. In typical Audi fashion, the fit and finish is superb, with generous amounts of wood, Alcantara and aluminum accents lending a luxurious ambience.

With a 16-way power-adjustable driver seat (including upper seatback angle) and a power tilt/telescoping steering wheel, finding a comfortable driving position is easy for folks of all body types. The dash is uncluttered by buttons thanks to Audi's MMI, which handles everything from the navigation and audio systems to the adjustment of the driver-selectable air suspension. And unlike BMW's iDrive, MMI doesn't require a Ph.D. in rocket science to operate, though cycling through the network of menus remains a labor-intensive process.