From what I've read on here, the Gintani Race's the loudest mufflers for an e9x M3. I'm sure others that have heard both in person can chime in as well. Although, I've heard a full Gintani race + X-pipe (no cats/resonators) in person & that thang's LOUD!!!
Wasn't really feeling it since it's more of a domestic v8 rumble compared to an F1 high-pitched sound (Meisterschaft). Not sure about Remus Race besides it being loud also.