I have the N1 on mine.
Personally i love the look of it and the sound.
i have it on with the apex 2.5 d/p and i think its perfect not too loud and not quiet definetly.
OrangeMSP has one on his car, altough his is the one with the custom turbo setup. I rode in the back recently and I literally could not hear them talking (even with music down) unless I leaned forward up into the front of the cabin. It's not *loud*, it's just a drone that gets a bit annoying when you're sitting right above it.