What years are you considering? I would definitley get the M3 regardless of year although the 03 M3 is the best. It is the fastest of the three you mentioned. The prelude is older and the RSX is not nearly as fast as an M3 of any year, I think. Be carefull of high mileage BMW's though. If you are talking high mileage cars, I'd go with the Preldude since there shouldn't be many high mileage RSX's anyway. Good luck.