I was torn between the KB kit and ATI and decided to go ATI on my 04GT. great numbers for your car.
I added the P1SC-2 with 3 core sheetmetal cooler, 75mm TB and TFS plenum, 42lb injectors, ATI solutions ProM meter, Aviator pump, and SCT tune to my stock motor and dynoed at 413rwhp 409tq. basically about a wash between our two cars in comparison but I was able to get some additional aftermarket parts with the grand + I saved getting the procharger.