By Samuel Ee

WHEN the most powerful road car Audi has ever built is stationary, there is only one outward indication of its phenomenal power.

Not the five-litre V10 direct injection engine with twin turbos, nor the understated estate body style, but the massive brake discs. The front ones are as big as manhole covers and especially eye-catching. Size really does matter. These ventilated cross-drilled discs have to be able to stop the big Audi if all its 508 horses are unleashed.

The Audi RS6 Avant may look like a sedate station wagon, but it is anything but. It is a sports car in disguise, a sleeper that will sprint from zero to 100 kmh in under five seconds, and on to 200 kmh below 15.

Under the bonnet is a V10 engine derived from the Lamborghini Gallardo (Audi and Lamborghini are both part of the Volkswagen Group). The only difference is the 5-litre unit in the Audi is even more powerful than the Gallardo's, thanks to turbocharging.

But like the Gallardo, the power of the bi-turbo direct injection engine is transmitted to all four wheels. The RS6 has Quattro permanent all-wheel-drive, and it is this feature that imparts confidence to the driver despite the prodigious power.

You may be driving into an afternoon thunderstorm on the PIE but the RS6 will feel supremely stable. Its huge 20-inch wheels simply slice through the rain-soaked tarmac and you can take that exit ramp corner at the same speed as you would on a sunny day.

The Quattro system normally splits power 40 per cent to the front wheels and 60 per cent to the back, with the slight rear bias chosen to enable sportier handling. Together with the sport suspension's ability to choose between three damper settings -comfort, dynamic and sport - the car can be pretty fun to drive.

Part of the driving pleasure is also down to the engine's huge lungs and the good steering feel. Unless you're on a race track, there will not be a moment when the RS6 feels like it doesn't have enough juice.

And unlike other souped-up Audis in the past, the RS6 serves up the power and torque (all 650 Nm of it) with a bit more attitude. The car is refined and luxurious, but the engine and exhaust noise is more audible than before.

With its high level of steering accuracy and feedback, you can point the Audi in the direction required, jab the gas pedal and it will hurtle forward instantaneously. Even at slightly over two tonnes, it still has the power-to-weight ratio of a sports coupe.

While the RS6 comes standard with a long list of equipment, one option to consider is the ceramic brake system. It provides bigger front discs and huge six-piston callipers for even better braking performance. As with all Audis, the RS6 Avant feels sturdy and well-built. It has heaviness that is both comforting and reassuring.

A sedan version will arrive early next year.

While neither body style will have the exotic looks of a mid-engine Lambo, it is worthwhile considering that both are about $300,000 less than the Italian supercar. Plus they can carry more people and luggage. So if you need a reason to buy the RS6, just think of it as a value-for-money Gallardo.

This article was first published in The Business Times on Oct 25, 2008.