i havent really been looking into turbos that much so if this question has been asked my bad..but is the only difference between the stage one and stage 2 of the hahn turbo the intercooler..and could a get a stage one and get a different intercooler and a later time..like a greddy or will it not fit..let me know thanks

Yes on the first question.

You can use any intercooler that will fit. Piping will be your only "custom" obstacle. For that, poeple have used madrel bent piping from JCWhitney and cut different pieces and used couplers.