If all you want to do is change the sound and assuming your existing pipes aren't all rusted out, just a muffler will be what you need. There are tons of exhaust clips out on youtube, that'd be your best bet to find the sound you want. I have a flowmaster 50 on my 4.0L and like the sound. Most "turbo" mufflers are going to give you about the same sound you have now, maybe little louder. Glass packs are just loud for the most part and IMO don't sound that great. A lot of people like Banks, including myself, but you pay for the name. Magnaflow's sound nice IMO, a little on the loud side if you have the straight through style.
There's my cent and a half!