for those of you looking for deep tone or just good looks, get an Arospeed muffler like I did. I have the dual outlet one that has a square-like circle bores. they sound fantastic and look GREAT. I paid like $250 installed. shop did it as I waited for 1 hour or less.
it's a deep tone and not too loud at all. I hate loud exhausts because it reminds me those annoying civics that are loud but don't accelerate...
as for performance, it feels that I lost the lower RPM torque as my P11 is a AT. high RPM is okay.