This is a good thread:
Bottom line, I wouldn't do it and not only because you have to replace parts. The M3 has a different braking system entirely (different master cylinder) ... who knows what kind of effect that will have on braking performance.
2011 BMW 335i E92 - Le Mans Blue, 6MT, M Sport. JRZ RS Pro, Quaife LSD, BMW Perf Exhaust