Manufacturer's figures (except in the case of the Italians) are always at least half a second on the pessimistic side (the Italians do it the other way round). The best source imo for 0-60 times is evo magazine, pretty much the bible as far as performance cars are concerned.
The comparitive 0-60 times according to the bible?
RS4 0-60 4.8 secs
RS6 0-60 4.8 secs
M3 CSL 0-60 4.5secs (4.2 was taken from the preview article)
Don't get me wrong I like Audis, and the RS models are obscene (if only they weren'y bloody estates), but M3's are in another league imo, and the CSL is one of the finest performance cars of all time imo.
Merry christmas anyway tho