Funny you should ask. I just finished doing some research on this.
If you need to, or want to, stay tree friendly, then the Bassani X-Pipe with cats seems to be the best option. (my option)
If you can get away with an off-road pipe then the Mac or BBK, H-pipe seems to be the best choice as far as overall torque and hp. If you go off-road, (no cats) don't forget to get the eliminators.
Either option is a good for quite a few HP(deffently worth the $$$), with a fairly easy install. Basically it comes down to the trees, and/or how hard it is to pass inspection in your area.