I'm running Dynomax Blackjacks designed for the Truck, they are 1 3/4" Primaries and 3" collectors, Running 2 1/2" Pipes all the way back, I had the muffler shop put on a Balance pipe, but I'm not sure if it helps since its back behind the Trans .

I'm using Walker Mufflers.
Its pretty Mellow at Idle and around town (still has that nice rumble, but once you get into the throttle it opens up and sounds really wicked, not overly loud, just a really vicious note.
Of course that was with a fairly mild Comp Cams (in the .485 lift range). The New Cam is a .585lift Roller unit... so I am sure that will change the sound dynamic.
I'm almost certain that Dual 3" would be overkill and kill some Low-end (and daddy loves Torque).