leave greddy out of whatever decision u make if u looking for anything above 300whp reliably...
reason being u'll be working the greddy turbo and components too much at those power levels for it to be reliable....the intercooler though will be fine
AJP kit is like the full race kit for the rsx....big power with options.
PS: the engine bay is not tight...there's actually more room in there than in the rsx