"It was the right car at the right time," said Reil. The go-faster station wagon stands out as one of the maker's most successful achievements and become steadily faster and more sophisticated since the first production version broke cover in summer 2002.
The story started when Audi built a small series of two extremely sporty station wagons, the RS2 and its successor, the RS4, at Porsche. But these were all based on the humble, mid-class Audi 80 and A4.
Basing the next model on the roomier A6 was the secret of a car that continues to fascinate right down to the current fourth generation.
The first RS6 to appear is already a classic, still able to make ample use of Germany's largely speed-deregulated autobahn motorways. The 4.2-litre engine delivers a satisfying growl from 450hp on tap and develops the sort of power normally reserved for racing cars in touring championships.
Down the years, the RS6 has had a variety of engines and the latest edition boasts a 4.0-litre twin turbo V8, thumping out 592 bhp through the eight-speed automatic transmission to all four wheels.
Behind the wheel the driver of gazes at an array of instruments illuminated in red. Dab the accelerator and the analogue needles twitch across the dials as the RS6 shows that it is raring to go.
Slip the autobox into D for drive and before the navigation system has finished building up its pixelated map on the palm-sized screen, this squat, elder sportsman is bounding towards the horizon. Within 4.7 seconds the RS6 is up to 100kph, thanks to maximum 560Nm of torque and permanent all-wheel drive.
Sporty estates with this kind of grunt were virtually unknown before the Audi bowed in and although the car was unlike any Avant which went before well-heeled punters took to it straight away.
The Bavarians planned to make only 999 but 8,000 RS6 Avants had been manufactured by 2004, said Reil. The car carried a price tag of nearly €90,000 (RM407,000).
The RS6 was a global success story and the Quattro GmbH division of the company decided to up the ante with a bonkers, twin-turbocharged V10 engine that was so massive that it hardly fitted under the bonnet. With a capacity of five litres, this was the daddy of all RS engines, with 580 horses on tap.
Reil and his colleagues eventually opted to tame the beast, adopting a strategy of "less is more" for its successor two years and 4,000 cars later. The made-over model went back to a V8 albeit with 560hp under the bonnet.
"But it was also a lot lighter," said Reil before a showing a stats sheet which lists how the changes improved performance and even made the car 30% per more economical than its predecessor. The third incarnation of the RS6 became a best-seller and stayed in the catalogue for five years.
Combining a more thrilling drive with the ability to take the kids to school, the RS6 is a winning formula for drivers who do not want a chunky SUV. At the same time, it has no green credentials either.
When the new A6 arrived in 2018, Quattro GmbH didn't wait long to launch the fourth and youngest RS6 in 2019. The car is wider and has more width and presence than ever and comes with a new version of the trusty V8 engine.
Even the entry model now produces 441 kW/600hp from four litres of displacement, and the RS6 plus has not even been presented yet. Meanwhile, the price has rocketed to €165,000 (RM746,000).
With four generations and over 20,000 units sold, the RS6 Avant is not only an important pillar in the portfolio of Quattro GmbH, which has since been renamed Audi Sport.
It has also left its mark on an entire segment, says classic car expert Frank Wilke from Classic Analytics.
"The BMW M5 had always been considered the business express par excellence but frequent drivers and travelling salesmen suddenly had the choice between the saloon with the kidney (BMW) and the Audi estate with the rings."
Audi Sport is now also moving towards electrification too, so that the current RS6 Avant will probably be the last of its kind.
However, as Audi's electric car offering grows, the Audi Sport arm will take full advantage of electric powertrains – including legends like the RS6.
Sport boss Sebastian Grams said the company is developing a new A6 for petrol-heads, which could become a green RS6 with a particularly powerful hybrid drive.
A future electric version may look a lot like the gorgeous A6 Avant e-Tron concept. This one could accommodate massive batteries, with claims of a 700km-range range and a sub four-second 0-100kph time.
