Originally Posted by Kev
Shell out another grand and get the Akrapovic full system
+1 - The Akrapovic full system seems to be highly praised if you have the $$$. Good performance, sound, quality, fit, finish, looks, everything.
The Dinan full system also very nice. Quality with no drone and moderate sound volume.
The Gintani full system produces great power but it is LOUD with the normal exhaust and still not exactly mellow with the sport exhaust.
There are other options out there but the (3) above are solid recommendations. Keep in mind all will require a tune to get rid of the CEL (check engine light) if you remove the cats like these full systems do. The tune will cost you about another $1K.
Also a 'full' system is from the headers back. You can also just do a x-pipe back system (cat-back as some call it).
Hope this helps.