The biggest difference between the SP1 and SP2 are the chassis length (4mm longer) and the rear shock shafts. Also they went from the blue springs to the dark blue springs. The rest is pretty much the same and you do have some very good hop ups already.
A WC will not be that much of a leap unless you really want to get a few Ti screws (phillips head, not hex) but essentially it is the same as the SP2.
A Chassis switch will neccesitate a longer rear center shaft too.