I was looking to liven up the sound on the cheap. The 2500's come with mandrel bent 3" from the factory, so I bought a 180deg mandrel bend and a short section of pipe, all stainless, and a Flowmaster Super10. I dropped the factory muffler and welded up an S-pipe, to duplicate the factory muffler offset, and stuck the Super10 in.
The outside sound was awesome, but the interior resonance was insane!! It actually hurt at about 1900rpm. So I ordered up a Pypes M-80, and put that in front of the Super10. The Pypes muffler kills the resonance and the Super10 depens the tone. I'm very happy with the combination. Interior sound is very good, but she still has a LOT of bark. (my neighbors love me
Put a nice 4" tip on the factory tail pipe and wala!!
Total cost, not as cheap as I had hoped.
I've got about $150 in it, but the sound ended up to be exactly what I was after, and everything is stainless, so it should last a long time.
The point is, on the 2500's you have a good system from the factory. I did pick up a half MPG or so, so efficency has been improved. Use what ya got, and just select the sound that you want.