Thanks, Lambo

Despite the heart of a raging bull, Audi AG's latest sport sedan, the S8, stands as the epitome of subdued excellence.

New for '07 in second-generation guise, the S8 is the high-performance variant of the auto maker's short-wheelbase A8 flagship. However, in place of the standard A8's 4.2L DOHC V-8 or 6L DOHC W-12 sits a snarling longitudinal 5.2L V-10 sourced from the Lamborghini Gallardo.

Audi purchased Sant' Agata, Italy-based Automobili Lamborghini SpA in 1998 and has since revitalized the hallowed sports car maker with fresh designs and improved quality and technology.

In the greater scheme of things, the S8 occupies a rarefied field. It is one of only a handful of large luxury barges to be outfitted for aggressive driving.

But outright performance is not the S8's forte. It's not brash enough to outgun an AMG Mercedes S-Class, nor is it exclusive enough to one-up a Bentley Continental Flying Spur at the local valet.

What the S8 offers is reserved style and performance — and loads of it. And at $94,420 (including destination and gas-guzzler taxes), it holds a significant cost advantage over its $100,000-plus rivals.

Garnished with moderate exterior changes, including a more aggressive front fascia, a chrome-accented grille and integrated rear spoiler, the only real clues to the S8's hidden muscle are its four oval exhaust outlets, a few discreet V-10 badges and unique 20-in., 7-spoke alloy wheels.

Monstrous 15-in. (38.1 cm) front brakes (13.2-in. [33.5 cm] units in the rear) and caliper blocks painted black with embossed S8 logos indicate prodigious stopping power from the 155-mph (249 km/h) electronically limited top speed, but are otherwise lost in the muted presence of the S8's design.

The all-aluminum, 5.2L DOHC V-10 has been enlarged from the Gallardo's 5L displacement to muster better low-end torque and drivability for the larger, heavier S8. Enhanced with Audi's FSI direct-injection gasoline technology, variable valve timing and variable length intake runners, the compact V-10 produces 450 hp and 398 lb.-ft. (540 Nm) of torque, 90% of which is available from 2,300 rpm.

The Gallardo's 5L V-10 produces 512 hp and 376 lb.-ft. (510 Nm) of torque.

Awakening the Italian beast under the hood evokes a subdued, yet throaty exhaust note that is instantly recognizable as coming from an odd-firing 10-cyl.

Under acceleration, the engine emits a warbling crescendo of mechanical melodies all the way to its 7,000-rpm power peak. On the road, where the standard quattro all-wheel drive and refined 6-speed Tiptronic automatic transmission come into play, the 4,586-lb. (2,080-kg) S8 can dash to 60 mph (97 km/h) in 4.9 seconds, Audi says.

Although not frighteningly quick, acceleration is linear, with big, smooth doses of shove coming with each gear change.

Track-ready the S8 is not, but its revised 4-link front/trapezoidal-link rear suspension with adaptive dampers does a commendable job of making the executive limousine feel much smaller than it is.

The driver-adjustable air suspension sits 0.8 ins. (20 mm) lower than the standard A8, and the softest setting is equivalent to the standard model's firmest sport setting.

The S8 glides over twisty mountain roads with little drama, consuming all but the largest potholes while maintaining considerable poise and comfort. Steering is direct and responsive (10% quicker than the A8) with good turn-in feel. However, on-center tracking is rather vague at steady highway speeds, and the front seats could use more lateral support in corners.

Understeer in tight bends is expected from any AWD vehicle with a big engine hanging partly over its front axle. However, Audi's new quattro system with a 40-60 front-rear torque split offers up a slight rear-drive bias that makes the S8 feel surprisingly playful.

Taking the already exquisite A8 interior to new levels, the cockpit of the S8 is highlighted by a fat steering wheel, Alcantara headliner, dark Birch Grey wood and an optional full leather upgrade with 2-tone, premium leather seats ($3,900).

The highlight of the interior is the audiophile-grade, 1,000-watt Bang & Olufsen stereo, a $6,300 option for which Audi is experiencing a near-100% take rate on initial S8 orders.

For those on a “budget,” Audi offers the midsize S6 sedan, also in second-generation form, for about $20,000 less than the S8.

Sporting a detuned, 435-hp version of the 5.2L V-10, along with nearly the same drivetrain, suspension and features as the S8, the S6 helps grow Audi's line of special S and RS models, while offering a slightly smaller and more nimble overall package.

Unique features to the S6 include 19-in., split 5-spoke wheels, as well as new sport seats that are supportive but a little firm on the backside. Dynamically, the S6 and S8 are nearly identical.

City/highway fuel economy for both cars is rated at 15 mpg (15.7 L/100 km) city and 21 mpg (11.2 L/100 km) highway. The S6 (base price $74,020), is available with many of the same options as the S8 and currently represents the top of the A6 lineup.

That is, until the second-generation RS6 debuts later in the decade packing a V-10 with some extra assist from twin turbochargers.