I average 23-24 in the summer, and 21-22 in the winter, depending on how hard I push the car. My driving is very mixed (highway, stop and go, back roads), so I think that's an honest number. I've seen up to 30 on highway slogs with the cruise set, and below 14 on a ... ah hem ... 'spirited tank'.
What I've found is that the fuel consumption seems to be linked to how hard you are pushing the car, and not really the RPMs - which I find a little strange, and doesn't really make sense to me.
And I'm glad the build thread could help - clubwrx has a lot of friendly and knowledgeable people. I've learned quite a bit in the process of doing this build, and even though the build was never really intended to go quite as far as it did, I'm glad I did it.