THERE’S a power struggle going on but it’s not taking place in the boardroom; it’s happening in the engine rooms of premium German estate cars. One of Audi’s key rivals has already taken the latest shot at become the top dog, but now the Ingolstadt firm has struck back with its RS6 Avant.

You don’t need an elephant’s memory to realise that RS models have never been short of power. The previous RS6 had a twin-turbo V10, and before that the it was a twin-turbo V8. No RS6 Avant has had anything less than 450bhp, which was a supercar-only figure just 20-odd years ago. This latest model has 552bhp, which sounds like sanctioned madness and damned good fun.

But this is the 21st Century where number chasing goes as far as fuel consumption and emissions as much as top speed. So the RS6 Avant’s blockbusting engine has cylinder-on-demand, which switches off half the engine under light loads in order to save fuel, and while that might seem irrelevant on a car this fast it helps it to achieve 40% better fuel consumption than the old car; 28.8mpg combined is possible.

And the RS6 remains just as much an Avant as the 2.0 TDI. Climb in the back and there is stacks of space, except instead of nice cloth you have even more tempting leather. There’s room for three adults too, so you can take four passengers and scare the living daylights out of them if the mood takes you. Out back there is that vast boot with divider rails and storage compartments, 565 litres of space with the seats up and 1,680 with them folded – Audi points out that the RS6 Avant is the world’s fastest production estate.

All the clues are there of course. It clearly has its roots in the A6 as you approach it but the visual muscle is hard to miss. Fractionally more subtle than the old car, it has the flared wings, the gaping front grilles and vast alloy wheels (20-inch standard, 21-inch optional). Models with the optional dynamic package even have ‘Quattro’ printed on the lower front grille.

Step inside and the chunky bucket seats greet you, offer a multitude of adjustment and are supremely supportive. The Audi Drive Select system is standard of course, but even when starting up in Comfort mode there is a charismatic rumble from the exhaust when you hit the starter button. Slot the gearlever into D and with the faintest brush of the throttle the RS6 gets going.

Even when behaving yourself in the first few miles the RS6 can’t hide how much power and torque is on offer. A moderate squeeze of the accelerator delivers thoroughly effortless acceleration in massive chunks, until you quickly run out of road. But it remains civilised with the standard air suspension doing an impressive job of smoothing out lumps, despite the big wheels, and the noise is muted. Back off the throttle quickly however and there’s a delicious crackle from the exhaust – just in case you’d forgotten what this car can really do.

Munich isn’t know for having miles of sinewy B-like roads, but what it does have is deresricted autobahn. Turning the Drive Select system to Dynamic primes the RS6 Avant for action; sharpening the throttle, gearbox and steering response, turning the exhaust to maximum volume and sharpening the suspension. Cruising with the traffic at an easy 80mph is still comfortable, but when the traffic peels away it’s the performance that steals the show.

Bury the throttle and it’s blasting forward instantaneously, the engine giving a controlled blare through its exhaust. Flip the right paddle on the red line and the surge continues again, accelerating seemingly as quick as it was 50mph ago. On several occasions in just a few miles the RS6 Avant ran to beyond 160mph with devastating ease, and hauled back down to a sub-100mph cruise with even less effort. The standard RS6 is limited to 155mph, but you can option a 174mph or even 189mph limiter – yet it would easily go beyond this given free reign.

And all that power is easily exploitable too, with the reassurance of four-wheel drive. Physically it is a big car but it all feels controlled and manageable from behind the wheel; sharp steering, composed suspension and immense brakes (with optional ceramic discs for greater power). If the RS6 can’t use it’s power, no car can.

You could argue that a car like this is frivolous, costing almost £80,000. But that would be to miss the point entirely. What other car can carry five adults plus stacks of luggage, cross countries in any weather and leave supercars at the lights as it blasts to 62mph in 3.9 seconds?

Audi RS6 Avant, £76,985
Engine: 4.0-litre petrol unit producing 552bhp and of torque
Transmission: Seven-speed dual clutch automatic driving all four wheels
Performance: Top speed 155mph (optionally 174mph or 189mph), 0-62mph in 3.9 seconds
Economy: 28.8mpg combined
Emissions: 229g/km