It all depends how far you want to go with it… ? …
Are you looking for a maximum effort motor…500 + ? hope you understand that may require clutch, transmission, shafts, diffs, housings, ect.
Are you looking for a fast fun street car that you can do pulls with once in a while?
Find out what the power limits/mod limits of the reflash are… and see if that is acceptable. In my opinion the reflash would be the best route at this point… Why?.. becaue the ecu is REALLY integrated into newer cars subsystems. Fucking around with a standalone can be HUGE… read: enormous and expensive… pain in the ass. The reflash is so nice and simple. Very attractive choice, if it meets your requirements, IMO
I was never a fan of piggybacks and signal interceptors but they are worth considering. Do research and talk to people with EXPERIENCE. Guys with cars putting down serious power… ask what they are running and how they like it… spend a hour a day emailing people… youd be surprised how much you can learn… most guys are helpful and will give you a honest perspective… not clouded by magazine editors and other bullshit