From what I've researched JBA seems to be a favorite for the $ & power gains. I've also looked into Magnaflow, Stillen, Banks & FlowMaster. Power gains all seem to be within a few hp between the diff systems, even JBA.
I talked with Kyle at Stillen & have decided on their system. I like the features of their exhaust and I'm not into loud obnoxious trucks. They also offer a dual side exit system in stainless steel unlike the others.