I did a 2013 M3 and modded it to 650 HP and also picked up a 2013 STi. But the alternative wouldn't have been an M5...it was a GTR or two year old 911T. Glad I did as the M3 has proved to be a GTR and 911T killer.
The M3 and M5 are two totally different cars. I don't think many people would cross shop these.