The B7 RS4 is a great car, I loved mine. Even though on the rollers they don't make the manufacturers quoted figures, they do on 0-60, 0-100 etc, so not a massive issue, but on an 80k car, Im sure there is some cleaning to be done internally (mine had only done 30k).
Just a couple of things to look out for; Discs and pads are expensive, from memory best part of £1000 an end from a dealer(maybe got cheaper now), and ours mostly did town journeys and averaged about 16-17mpg, which was painful 5 years ago when fuel was a lot cheaper. However they are an awesome bit of kit, great road holding and road presence, and the noise is just phenomenal, and I would advise investing in a cat back Milltek.
Point to point, in any weather, there are not many cars that are going to pull away from one, or get anywhere quicker, especially with the load capacity that and RS4 has!
Good luck, and go for it