Originally posted by westcoaststyle
I've heard that the Greddy Evo is the quitest on the market. My buddy has it on his car and it's very clean and quiet. I'd say stay away from the Apexi products (N1, Dunk) as they are extremely loud.
I know you and I don't get along, but I'm a dealer for this stuff so if you want some pricing on it, PM me and we'll see what we can do.
Good question BTW. 
there is one apexi exhaust that is really quiet, did u forget about the world sport? i have that on my car and its VERY quiet.