I just had a Flowmaster Super 40 intalled on mine yesterday. I'm extemely happy with the tone I got, its deep and throaty, without being too loud and obnoxious.. But mine is a 4.0L, I have no idea how it would sound on yours.
I've seen mentioned on this forum that You-tube has some video comparing different exhaust systems. The only thing I can suggest is to use the search function and type in "You -Tube exhaust comparisions" or some such thing to find them. Sorry I can't remember all the particulars, but maybe the moderators can.