To answer your question though, I'd say a fair-to-semi-ambitious guess is up to 3/4 sec faster than a stock WRX. With those parts, you may even pick up a second over stock. So, if a stock WRX runs 13.9 - 15.9, you could possibly run 13.3-15.3 or maybe even break into the
very high 12s if conditions are absolutely ideal and the wind is blowing at your back. How's that?
Honestly though, there's really no telling just based on a description of parts. If you want a real number, I agree with Joshua - take it to the track and find out.