I just bought a Thrush Welded Muffler. It'll be pretty dang loud on a dual setup. It's loud on my 2.5" single setup. Sounds like a flowmaster but with a tad less of the "tinny" quality, though it still has that. I think the one I bought was at Advance and was $30-$35 or so.
Here's a bad video of it to help you judge the sound and volume... the exhaust exits on the drivers side of the truck and it's still loud. I don't know about in the cab resonance. I have my cab sound deadened so good with the windows up its silent...
Thrush Welded Chambered 2.5" single