Driving
Using an enlarged version of Lamborghini's V10, the S6 produces a mighty 429bhp. Although that lags 78bhp behind the BMW M5, it's worth noting that not only does the S6 produce more torque, but its power is delivered further down the rev range. This means it's an effortlessly fast car - even if ultimate acceleration isn't nearly as savage as the M5's. Unlike the BMW there are no steps in the power delivery; it's smoother and sounds superb. There are flaws, though. The throttle is too sensitive on light openings, the six-speed Tiptronic auto is slow to change down and the manual mode doesn't give the driver full control. Considering this is the most driver-focused version of the A6, it's no surprise that the Audi rides much more like a sports car. Given the comparative softness of the RS4, we expected the A6's suspension to be absorbent, but in reality it proved extremely crashy and bumpy. It is fine on smooth surfaces, where it proves great at high-speed cruising - thee only noise is from the burbling V10. However, while rough tarmac failed to throw the car off line, it did cause shocks to enter the cabin. This contributed to the feeling that the Audi just doesn't have the same rigidity as an M5. But stability and traction are superb, and the A6 fails to be upset by wet weather.

Marketplace
Historically, Audi's hot saloons have tended to be speedy, safe and secure, but ultimately rather lacking in excitement and involvement. The charismatic RS4 changed all that - and now it's the turn of the S6 to prove it wasn't a one-off. On paper, it looks promising, thanks to Lamborghini input, and nor is it a letdown in the flesh. The ordinary A6 is stylish, but this version, with its flared front wheelarches, aluminium door mirrors, LED running lights, 19-inch alloys and a unique grille, is something else. Subtle and purposeful, it looks fantastic. As mentioned, the S6's deadly rival is BMW's M5, also using a large-capacity V10 engine.

Owning
Immaculately constructed, beautifully laid out and effortlessly easy to live with, the S6's cabin is extremely impressive. It's just a pity that it's not a bit more sporting. Aside from carbon fibre trim on the console, silver paddles for the gearshift, subtle badging and the superb sports seats with built-in headrests, it doesn't quite do enough to make you feel like you're in a car that's truly special. Nevertheless, the A6 is comfortable and luxurious, and as it's likely to be used as daily transport, that's arguably more important. Certainly Audi has ensured practicality hasn't suffered. The giant 546-litre boot is the same size as on lesser A6s, and the rear seats are nearly as cosseting as those up front. It's thirsty though, averaging 18.7mpg during our test, while residuals lag behind its key rival. At least servicing costs don't look too excessive.