I'll met you in the middle and just say toss on a big 16g for the wrx and detune it. Then toss on a td-06 18g and detune it for the sti. Both can hold decent boost till redline, and be tuned for longevity. All it would take is a protune to be pushing MAJOR power on each motor.
How does the vf-41 (Legacy GT turbo) do on the 2.5?