I just bought a GXP and really like it. it rides way better than my GTP. the GXP makes about 250 hp at the wheels in stock form, and with a few mods you can get 300 hp at the wheels. I turned off Dod/AFM in the tune so it shouldn't fail as fast as it normally would. with a shift kit and an aftermarket trans cooler the transmission should last longer. my plan for modding to get the 300 hp at the wheels is an overkill tune, an E85/flex fuel kit, upgraded maf sensor, and an LS6 intake manifold swap, and bigger injectors to give the E85 more headroom. all of that will cost about 1200, less if you don't buy the kits from overkill and if you can find a good deal on the LS6 manifold, and you can also do a truck intake manifold for a lot less.
I chose 300 hp at the wheels because that is about how much the transmission can handle and seems to be the happy medium for power per dollar. with a little head work and a cam the LS4 will make 450 hp at the wheels pretty easily.
