Just as a note on the RS4 running costs, in the 7 months/7000 miles I had mine, it averaged approx 16mpg, and went through tyres like its going out of fashion and the brakes are around £2000 fitted allround(I had to replace mine). They are a fantastic car but with very high running costs, and I wouldn't consider one unless it had an Audi extended warranty, as the engine alone is over £10k if it went pop!
As for the Golf R, I had one on provisional order for three years, when the rumours of the R36 were about, and I cancelled my order as they are just too bloody expensive! Nuff said!