I honestly think you should leave the M stock or max. with bolt on upgrades. The reason is because you say you use it as your daily drive and already having the R8 V10 and 430 Scuderia I see no real point in taking the risk...
However if you are 100% set for a big tune, get RD or Dinan stroker. 1) they seem more reliable and offer good warranty. Since that's what you are highly concerned about (and you are very right to do so), it's a big +. 2) was considering SC from GPower before myself because I have to admit, I do love turbos/SC
but honestly everytime I hit the pedal on the M3, knowing all that power comes from a NA engine makes me feel more satisfied, which is why I might go for Dinan in a couple of years if I get bored of stock M although I doubt it
!