If you're not wanting to cut into your bed, but get more travel and performance than bolt in 3.0s, you have 3 options that I know about. Icon's RXT setup, Rogue's cantilever setup and RPG's rst16. Don't quote me on these numbers, but I think they're 16", 20" and 18.5" respectively of rear travel. Icon and Rogue utilize 3.0 and RPG use 3.5 5 tube bypass. All 3 are proven great options.
RST16 is 16" travel. RST18 is 18" travel. Cantilever is 18" of travel also - just has the advantage of not using up bed space to get the travel. You can't go wrong with any option really. It will all boil down to your budget and how comfortable you are with cutting into your truck.