The Audi A6 is every bit as capable as the lithe, athletic look implies. A solid structure, good suspension tuning, and free-revving engines deliver excellent performance, and all but front-drive 3.2-liter model benefit from the most recent iteration of Audi's quattro all-wheel-drive system.

The A6 ride is firm but elastic, with large dips and sharp speed bumps managed well. It's among the best in class in comfort and near the top of its class in handling, notably bettered only by a rear-drive BMW. Regardless of which model you choose and its ultimate level of grip, predictable handling characteristics provide confidence.

Ride quality varies with tire choice, with the optional 19-inch wheels less forgiving over sharp bumps, lane divider dots and so on. We prefer the 18-inch wheels and tires and do not advocate the 19s for year-round driving in the Rust Belt.

The Servotronic steering allows precise control and the A6 goes exactly where the driver wants it. Grip is excellent. Drive the car to its limit and you'll encounter a small amount of understeer. The Avant exhibits the same characteristics though enthusiast drivers often feel the extra rear weight better balances the car. The highly rigid chassis gives the car the feeling of being carved from one block of material. This rigidity allowed Audi engineers to precisely tune the suspension. The A6 uses Audi's proven four-link front suspension and the self-tracking trapezoidal-link rear suspension adapted from the A8.

The new-for-2010 3.2-liter V6 (replacing the previous 3.2-liter) is all-aluminum in construction and fueled by direct injection. Aided by Audi's Valvelift system (continuously variable valve timing, with two-stage intake valve lift) it develops 265 horsepower, 10 more than its predecessor, while squeezing one more highway mile out of every gallon of Premium. Peak torque remains the same, 243 pound-feet at 3250 rpm, so the A6 3.2 retains its edge over BMW's lighter 528i, which rates just 200 pound-feet, albeit at a lower 2750 rpm. Audi says the 2010 A6 3.2 can accelerate from 0-60 mph in 6.9 seconds, same as the 2009 model. The CVT may initially feel or sound odd to those unfamiliar with one, but it's ideal for the best blend of performance and fuel economy.

The 3.0T 3.0-liter supercharged V6 gives up just 2 mpg EPA highway to the 3.2, but adds 35 horsepower and 67 pound-feet of torque and delivers the torque over a broad range, 2500-5100 rpm. This would be too much for front-wheel drive to cope with, hence all 3.0T models employ quattro all-wheel drive.

The quattro system, revised for 2009, has a more rear-bias nominal power split of 40 percent front/60 percent rear to make the all-wheel drive feel and respond more like a rear-wheel-drive car. Still, the A6 never feels nor responds exactly like a rear-drive car.

The added power translates to a one-second drop in 0-60 mph time, which Audi quotes at 5.9 seconds. The engine is as smooth and quiet as the 3.2, so you find yourself inching up the speedometer more easily. Perhaps just as important, the 300-horsepower, 310 pound-feet ratings put Audi on par with BMW's 300/300-rated twin-turbo 3-liter in the more-expensive 535xi sedan and wagon.

The silky 4.2-liter V8 produces 350 horsepower and 325 pound-feet of torque, and comes with larger brakes to go with it. The 4.2 is just 0.1 second quicker to 60 mph than the 3.0T because of extra weight in features and equipment and only slightly better torque than the 3.0T. Still the 4.2 gives up 2-3 mpg to the 3.0T.

All transmissions offer three shift modes. The standard mode is more than adequate for the majority of circumstances, and ideal for inclement weather. Sport mode is best for those more concerned with performance than economy or for limiting shifting over undulating and winding roads. Manual mode lets the driver choose gears, although it will still upshift or downshift automatically if you reach the engine's limits; that strategy may not satisfy purists, but it's handy when you forget you've left it in Manual mode. All the gearboxes shift smoothly and rev-match downshifts under certain circumstances.

The S6 features a 435-hp version of the 5.2-liter V10 engine used in the S8. With nearly 400 pound-feet of torque across the middle rev range and quattro to put the power down, we've done 0-60 mph in an S6 in less than 5 seconds, in the rain. Fuel economy ratings drop to 14/19 mpg, however.

The S6 gets massive brakes, nearly 1.5 inches larger in diameter than the already arresting 4.2 V8, sticky 265/35ZR19 tires, firmer suspension, aerodynamics to keep it grounded at 150 mph, the best lights, and seats to keep you in place while you use it all. And while the S6 is certainly firm, the kind of firm where you would rather be the driver than the passenger, it is docile enough to drive everyday, in traffic, if necessary.

The S6 competes with the BMW M5, Mercedes E63 AMG, and with the Lexus IS-F, Jaguar XFR, and Cadillac CTS-V. The ride and handling prowess of an M5 doesn't come cheap, with a base price $10,000 beyond the S6, while the CTS-V offers the best bang for the buck. Many of the other cars are faster and handle better, but none of them offer the space of the S6 nor the all-wheel drive that will put the power down in poor conditions.