But now the Sedan is on its way, and with its giant 5.0-litre twin-turbo V10 engine and quattro permanent all-wheel drive, we are not sure if we should be excited or scared.
When the German powerhouse says the sedan behaves like a supercar with the utility of a large executive vehicle, they are not kidding. As if a 5.0-litre V10 wasn't enough, they've strapped technologies like FSI direct fuel injection, dry-sump lubrication and not one, but two turbochargers.
With up to 1.6 bar of boost pressure (23 PSI), the state of the art engine delivers 650 Nm of torque, which comes in all the way from 1,500 to 6,250 rpm. But since this isn't a diesel, power is also exceptional at 426 kW (between 6,250 rpm - 6,700 rpm).
The might of the V10 is handled by a new auto six-speed tiptronic, which also allows for manual gear changes either using the shift lever or the paddles on the steering wheel. The car is driven via all four-wheels, however, being trademark Quattro, it's more rear-weighted.
All those numbers mean the 4.93 metre long RS 6 sedan can go from 0 to 100 km/h in a supercar beating 4.5 seconds. Top speed is electronically-limited to 250 km/h.
Numbers and acceleration apart, it wouldn't behave like a supercar if it didn't handle like one. Starting at the front, each wheel receives four (yes, four per wheel) lightweight aluminium control arms.
Going hot into a corner, Audi’s Dynamic Ride Control DRC reduces pitch and roll using purely mechanical means. The system uses hydraulic lines and valves connected diagonally to opposed pairs of shock absorbers. During enthusiastic cornering, the flow of fluid to the damper of the compressing outside front wheel increases, providing firmer support and reducing roll.
The car's DRC offers a choice of three selectable damper settings – sport, dynamic and comfort. Audi has also tuned the ESP to be a little forgiving, allowing for a "dynamic driving style". It also offers a Sport mode and can further be deactivated entirely.
Australian specifications list the RS 6 sedan as coming standard with 20-inch alloy wheels shod with 275/35 tyres. Brakes are nothing short of spectacular, with six-piston fixed aluminum calipers at the front clamping down on 390 mm brake disks (same size as the Aston Martin DBS).
The rear brake disks are still enormous at 356 mm in diameter and supported with single-piston floating brake calipers.
Being able to spot the difference between the A6/S6 and the might RS 6 might seem a little difficult for some (perhaps a benefit to the car's sleeper image), but those in the know can easily spot the single-frame grille, the large air intakes, xenon plus headlights, adaptive light and RS 6-specific LED daytime running lights, the flared fenders and deep side skirts, the rear diffuser, the spoiler integrated into the trunk lid and the two large oval exhaust pipes.
Getting inside any RS model in Audi's lineup has a Lamborghini feel to it. The company says the RS 6 is the embodiment of power, elegance, exclusivity and perfection. Some of the interior highlights include carbon fibre inlays as a standard feature (with brushed aluminium or highly-polished black lacquer as ‘no cost’ options) for Australian-built cars, and Silk Nappa RS-embossed leather seats in tried-and-tested Audi quality.
The full list of standard equipment will be available closer to the car's Australian release around the first quarter of 2009, but Audi says the RS 6 will receive the company's MMI (Multi Media Interface) system with a colour monitor and TV reception (analog and digital), advanced key entry, electric glass sunroof, Audi Navigation, dual-zone deluxe automatic air conditioning plus, an acoustic parking assistant at front and rear, a 3-spoke, multifunction leather sports steering wheel with flat-bottomed rim and a Bose surround sound system.
Additionally there will also be a boost pressure indicator for the two turbochargers in the driver information system.
Audi previously sold the last generation RS 6 in 2004 for about $220,000 for the sedan and $225,000 for the wagon. Pricing for the new RS 6 sedan is still to be confirmed.