suspension

I own a 1997 chevy K2500 x-cab 4x4. I already have a 3" body lift on it. Now I want a 5,6,or7" suspension lift on it. I have been looking at different suspension lifts for a while now but cannot decide which one to get. (rides smooth, and is built to last)

So I want to know out of all the brands out there, which one is the best and most highly recommended.

Thanks for any help y'all can provide!!!