In the heady world of the ultra-luxury sport sedan, the 2007 Audi S8 stands proud. Like Mercedes-Benz's AMG and BMW's M divisions, Audi's S group serves as the company's in-house tuning firm. Over the past decade or so, Audi's "S" has become a respected badge among enthusiasts.

Based on the standard-wheelbase A8 (as opposed to the longer "L" version), the S8 boasts a V10 engine borrowed from the Lamborghini Gallardo. The V10 sends its power to all four wheels via a six-speed automatic transmission. With 450 horsepower, it's not quite as powerful as it is in the Lambo, as it gives up some peak output for a broader powerband that's better suited to a luxury car.

Audi buffs will also know that this same engine is used in the company's S6 and is rated at 435 hp in that application. Even though the S8 is longer than the S6, it's lighter by some 200 pounds thanks to its virtually all-aluminum construction. As a result, the senior Audi should be quicker than the midsizer -- Audi claims a 5-seconds-flat 0-60-mph time for the S8.

In addition to the V10, the 2007 Audi S8 features a sport-tuned adjustable air suspension, 20-inch alloy wheels, upgraded brakes, unique front and rear fascias and front sport seats with 16-way power adjustment.

Of course, potential buyers will want to know which other ultra luxury sport sedans they should consider, and the truth is that serious driving enthusiasts would be better served by the BMW M5, which boasts blistering performance, sports-car handling and the availability of a manual gearbox. Those who aren't as into hard driving and who prefer an old-world luxury car feel may consider the Jaguar XJR, a still speedy sedan with an overtly plush cabin. The Maserati Quattroporte is another strong choice, with its Italian styling flair and sonorous V8. Mercedes' S65 AMG offers astounding performance (over 600 hp and more than 700 lb-ft) but it's about twice the price of the $92,000 S8.

In essence, the 2007 Audi S8 lies somewhere in the middle of this group, not as sporty as the Bimmer but more so than the Jag. This is a fantastic group of cars and in this segment it's often a matter of fine degrees or simply styling preferences that sway one's decision. Drive any that strike your fancy before spending the big bucks.

The 2007 Audi S8 is a high-performance version of Audi's A8 luxury sedan. It comes in one loaded trim level. Standard on the S8 are unique front and rear fascias, 20-inch alloy wheels, bi-xenon adaptive HID headlights, full power accessories, dual-zone automatic climate control, a navigation system and Bluetooth connectivity. Additional standard features include a sunroof, a power tilt-telescoping steering wheel, a trip computer, auto-dimming mirrors, two-tone leather seating, heated/power front seats and a Bose audio system with glovebox-mounted CD changer.

Options include keyless starting, adaptive cruise control, rear climate control, a premium Bang & Olufsen audio system, front and rear park assist with a back-up camera, satellite radio, power door-close assist, rear heated seats and a power rear sunshade.

Powering the Audi S8 is a 5.2-liter V10 with 450 hp and 398 pound-feet of torque. It sends its power to all four wheels through a six-speed Tiptronic automatic transmission that allows manual gearchanges via paddles behind the steering wheel. Audi claims a 0-60-mph time of 5.0 seconds and top speed is electronically limited to 155 mph.

Antilock disc brakes, stability control, a tire-pressure monitor and a full array of airbags (side curtain, front-seat side, rear-seat side and dual front knee) are all standard. A front and rear park-assist system is optional.

The V10 engine has a strong pull from just off idle through to redline – it really has no weak spots. The downside of such a stout, linear power curve is that there's no thrilling point where it suddenly takes off. The automatic's gearchanges are smooth and quick, though there's some hesitation when a downshift is called for. The S8's power is best manipulated manually through the steering-wheel shift paddles, something enthusiasts will no doubt enjoy.

The S8 rides slightly lower on a sportier variation of the A8's adaptive air suspension. It still offers four suspension profiles to choose from -- Automatic, Comfort, Dynamic and Lift -- but each level rides a bit firmer compared to the standard A8 setup. In any mode, the handling is confident with virtually no body roll, and the ride quality is impressive, especially for a car sporting 20-inch cast-aluminum wheels.

The only weakness in the 2007 Audi S8's dynamic armor is the brake pedal feel. Though certainly capable stoppers, the brakes' pedal feel is too soft initially, and somewhat out of step with the solid, confidence-inspiring sensation of the chassis as a whole.

Alcantara covers the roof and rear package shelf, while leather, aluminum and birch accents fill the rest of the Audi S8's sumptuous cabin. Double-paned side windows contribute to the hushed cabin while the 16-way adjustable sport seats provide long-trip comfort and twisty road support in equal measure. Audi's MMI (Multi Media Interface) control for the climate and audio systems is fairly intuitive, unlike the systems in its homeland competitors. Trunk capacity stands at 15 cubic feet, while a ski pass-through adds versatility.