??????and what exactly is a cat-back?

Later

 

A Cat-back exhaust means that the exhaust has been replaced from the catalytic converter all the way to the exits. The stock exhaust is restrictive for flow, and a cat-back usually results in better performance as well as a nice sounding truck (or car).

As for your question about what sounds good, use the search feature. You should find all the info that you need and then some. I happen to like straight pipes, but I have a V8, so I suspect it will sound very different from your truck. And there's even a difference between the 4.6 and the 5.4 motors as well.

Good luck.