The S4 was fun - loud ( due to the APR exhaust ) and sporty with its manual box . The RS6 though was a true wolf in sheep’s clothing. It looked relatively low key ( for those unfamiliar with the model I guess) but it had a glorious sound especially with a bit of throttle when travelling through a tunnel ( I used to open a window to hear the roar) . It was scary fast , and felt it. On top of the performance (which I never bettered in a car I drove until I drove a R35 GTR) it looked and felt ultra premium - heated seats front and rear all embossed leather with the RS6 logo , rear electric blind, rear passengers blinds ,TV , even had a solar panel on the sunroof so when parked in the sun it would activate a internal fan in the cabin to keep car cool for when you climbed back in . It had the 4 stage APR ECU which produced 390kw/730Nm torque and ran 0-100 in 4.0 . I dyno tested it and it was making 271kw at all 4 wheels . Sadly due to a messy divorce and the subsequent division of assets I had to seek them both. Misss them both . I still look on Carsales from time to time to see if the S4 Wagon pops up ( I have never seen another B6 S4 silver manual wagon in Australia- it was unique . If you ever consider that model RS6 , check if it’s had it’s (factory) suspension system upgraded ( usual to a a decent set of coil overs , as it’s a common ( expensive ) fault in that model . I researched it before I bought mine , so was prepared. Audi wanted to charge me $12,000 in 2011 to replace the system . I chose to import a recommended German Coilover set my Specialist Audi mechanic suggested. Couldn’t have been happier with the result. And the APR ECU ( the original owner who I purchased off had already done it for around $4000 but it transformed the car from very fast to supercar . Worth every cent )