If you're throwing boost at it, best look into the bottom end as well. I don't know how the rotating assembly will hold up to boost, most specifically the pistons and rods. You may not have to worry too much about the crank, but pistons, rings, and rods definitely.
If you only do the head and the bolt ons, no forced induction, here's how it should turn out:
You'll get more torque out of the bottom end because the air is more freely moving through the engine. The car will likely run smoother, albeit noisier (a good thing if you ask me, lol) Top end will feel more free and revvy, you'll probably find yourself winding it out further than normal because it's fun and sounds good.
Looking for numbers? No way to tell, really, without a dyno. Off-the-hip, I'd say perhaps anywhere between 15-20whp in the lower rpm band and 10-25whp in the top end. It's not a huge number gain, but gaining in the bottom AND the top makes the entire drive feel crazy fast.By comparison, of course.
Especially if you can find another car with a similar setup to what you have now (pre-mods).
Proof: I put on a pully and I only gained about 25whp at 7000rpm. I however, gained about 60whp from 2000 to 3500. Holy frijoles! That thing killed! I only had 249whp but was beating all the 300-350whp cars that I met. Why? they were turbo cars. They got all their power from 4-7krpm. I got my power starting from 2k. they were always playing catch up.
However you build, make sure you get your power throughout the rev band, not just at the top.