We'd had prior warning that Audi was planning to draw fresh attention to the nose of its cars through the Nuvolari concept and the A8 W12, but it's hard not to be taken aback when confronted by a grille the size of a bungalow on the front of what was - barring the RS6 - Audi's frumpiest model, the A6.

To be fair to the all-new A6, that eye-grabbing grille isn't quite so in-yer-face, as it were, when you see it in the tin; photographs lead you straight to it, whereas when you approach the car for the first time it's the size of the whole car that claims your gaze. In growing up the new A6 has also grown out, in length, width and wheelbase, moving to the top of the class for sheer presence. Catch the A6 out of the corner of your eye and it's easy to mistake it for the larger A8, though there are obvious differences when you see them side-by-side.

What Audi really wants, however, is for the A6 to be seen alongside, and preferably in front of, the BMW 5-series and Mercedes E-class. To date it has dynamically trailed its German rivals and the task of the all-new version is to convince wavering senior management that the 'third way' is now the best way.

You need only pull open the new A6's door to feel the amount of investment that has gone into this project; the door is heavy and shuts with an authoritative thwump. Once inside you're entombed in a plush world of richly finished wood, precision-movement switchgear and an overwhelming sense of being beautifully looked after. Audi's cabin designers really know their stuff; they've even managed to make the Multi-Media Interface (Audi's version of iDrive) work in a wholly intelligible manner. Passengers will appreciate the swollen dimensions as they now have room to slouch in the back; there's even decent provision for the piggy in the middle.

New A6, new engines. At the bottom of the pile is a 177bhp 2.4-litre V6 petrol, then comes a 3-litre V6 turbodiesel with 225bhp and 332lb ft of torque; up another rung is another petrol V6, this time a 3.2-litre FSI unit boasting 255bhp, while at the top of the family tree sits a new 335bhp 4.2-litre V8 from the smaller S4 model. Although not yet confirmed, a twin-turbo V8 S6 and a new RS6 running a detuned Lamborghini Gallardo V10 could join the range later (News, 066).

Like its predecessor, also a 4.2-litre but with 35 fewer ponies, this V8 is big-hearted in a laid-back sort of way. Gun it and it growls like a muscle-car motor, back off the gas and you can barely hear it - nicely schizo. And the way it sounds is the way it goes. Throttle on the carpet suggests the claimed 6.1sec 0-62mph time is no fantasy figure, but tread more gently and you can find yourself, without forethought or even awareness, deep into three-figure speeds.

The transmission - a six-speed Tiptronic with steering wheel paddles as well as a conventional auto lever - aids the deception, oozing its way up and down the ratios without pause or hesitation. As a result of the drivetrain's suaveness you might find the new V8 A6 short on raw thrills, but then that's not really its purpose. Mind you, chassis improvements have narrowed, though not closed the gap on the Five and the E. Most notably, the steering - bane of most Audis - now has a more satisfying feel, if no real intimacy. And the ride is less spiky, even with the sporting spring and damper settings of the 4.2, thanks in part to a bodyshell that torsionally is 34 per cent more rigid than its forebear.

Handling? Hard to pass definitive judgment on our German test route. As ever, the four-wheel-drive system lacks the finesse of the rear-drive 5-series once the corners turn to hairpins, yet on 100mph open sweepers you can feel the front tyres biting into the tarmac, lending you the confidence to maintain your headlong charge to the corner's exit.

British roads will decide whether or not the top-tier A6 is just all mouth and trousers, but there's no doubting its appeal. Spacious, luxurious and seriously bloody quick - not to mention attractively priced and equipped - it's hardly lacking fast-executive credentials.