See if you can get your hands on a 7AFE bottom end, and a 4AGE top end (silver top preferable). Put the 4age 20v head on the 7afe bottom, gives you a 7age (1.8L 20 valve engine). Slap a TD05 (start small, unless you want to go for a T66 GReddy off an older STi or similar), and she'll be good to 8,000 rpm with pretty much stock internals, and make about 350hp (give or take).
If you were to change the con rods and pistons, and possibly the crank (Don't really see why, the 7AFE crank is pretty good, the con rods are crap!), you could bump the revs up a bit, and the boost, and see yourself well over 400 (Or so the estimates go!)
Found this on some guys website, it's a "mock dyno reading", but should prove pretty realistic in practise
http://www.billzilla.org/7agepower.jpg