As M is to BMW and AMG is to Mercedes, so S is to Audi. What do all these big, scary letters mean? They're performance-tuned versions of Germany's finest, bringing a keener shine to already bright constellations. The S6 Avant is no exception, and we applaud Audi's decision to crank up the volume on a station wagon, once construed only as a bland family vehicle.

Propelling the S6 is a highly massaged version of Audi's 4.2-liter V8.Fiddling with the intake timing increases its horsepower output from 300 to 340 at 7,000 rpm. Plus, 310 pound-feet of torque peaking at a low 3,400 rpm results in a powerplant that Audi claims should be good for mid-6 second zero to 60 acceleration runs. The thundering hooves are doled out by a five-speed Tiptronic transmission with steering wheel-mounted controls.

Otherwise, what comprises the difference between the S6 and the A6? Aside from visual distinctions such as aluminum trim on the front grille, roof rails and side mirrors and the option to outfit the interior with special seat inserts, the S6 sports an all-aluminum suspension that whittles 24 pounds of weight. Springs are tauter by 30 percent while shocks have 40 percent increased damping compression, and its stance is lowered by one centimeter. It sports beefier brakes, and fatter diameter stabilizer bars keep body roll to a minimum. The 17-inch cast-alloy wheels ride on wide Z-rated tires.

Safety equipment that stands guard to keep you from going overboard in the S6 Avant includes front and rear side airbags, side curtain airbags, Electronic Stabilization Program (ESP) with a traction control system, and ABS with brake assist. Of course, the S6 Avant comes with Audi's quattro all-wheel drive system which utilizes a Torsen center differential to ensure the greatest amount of traction on slippery roads.

Standard equipment includes a premium stereo system with an in-dash six-disc CD changer; dual-zone climate control; power seats with heat, memory and lumbar support; a tilt/telescoping steering wheel that tilts away upon exiting; and an anti-theft alarm system. And you can't forget the 36.4 cubic feet of cargo capacity with the rear seat up and 73.2 cubic feet when the rear seat isn't utilized.

Available as options are high- and low-beam xenon headlamps, Alcantara leather trim, a navigation system, a rear parking sensor and heated rear seats. Nemo Blue is an S6-specific color that you can choose. Later in the year Audi will offer an OnStar telematics system with a digital telephone and Web browser. Audi offers four-year/50,000-mile free scheduled maintenance and roadside assistance for the same period.

Piloting an S6 Avant, Clark Griswold would have no trouble catching up to the hot blonde in the red sports car. We think that those who need to haul stuff and people also deserve to have some fun. Drivers rejoice.