ive gone through those 3 setups. as far as bang for the buck, if you dont need the bling factor of the 4/2, and are running 17" wheels, the setup from a 2005 Legacy GT turbo may suit you the best.
the sti rear 2 pot is a waste of money imo, it looks nice though.
i like the front subaru 4 pistons, its inexpensive and pretty good. my current brembo setup is unfadable (on my car), but rather pricey.
if going tracking, save up some dough and consult the guys at stoptech. they will make you stop fast.