This is the muffler I used for a dual exahust
www.FixThisRide.com - Flowmaster 524554 50 Series Suv/Perf 2.25
I had them install an X-pipe right after the collectors for better sound and improved flow. I've attached a word document that shows the diagram that the shop used (with the exceptions of an x-pipe instead of the h-pipe). Out the door was 300$ and it sounds nice. Quiet inside with a nice rumble when cruising. You can definitely tell when you step on it.