If you want it to be not so loud, then I would stay away from canister style exhausts. These include the A'PEXi N1, Tanabe Racing Medalion, HKS Hiper, 5Zigen Fireball, skunk2 Mega Power, etc.

Personally I go for an exhaust with an oval muffler with a not too big tip, and full stainless pipes. Examples of this "format" are RS*R Exmag, GReddy SP2, Tanabe Super Hyper Medalion, DC Sports, Comptech, etc.