We put the 2.5 inch exhaust from FWD on the GLH along with a Jones single chamber muffler andno cat. It's more of a flame arrestor than a muffler.
http://www.summitracing.com/parts/JEX-FB426/


I like the sound so far. It hasn't really been on the road more than a few blocks so I don't know if it has any drone to it. My guess is it will.
One issue was that once everything was bolted on and hung, the car vibrated like mad. I added a flex connector to the down pipe and that has seemed to take car of a lot of the vibration. The rest is the trade off for putting all poly bushings on the engine and trans.
http://www.summitracing.com/parts/JEX-FLX2508B/

Here's a video of the sound at the exhaust tip.
http://gallery.me.com/ajakeski#10013...&bgcolor=black