well, boost level means dick.
10 psi on a 14g makes say, 100 horse
10 psi on a t88 makes say, 600 horse
just generic numbers... but the size of the turbo has a LOT to do with power. people who say "I want to run X psi" clearly know nothing about turbos. hello and welcome to the internet

let's learn.
200 whp in a civic is fast
300 whp in a civic is stupid fast
400 whp in a civic is retarded
500 whp in a civic takes 30% off the average lifespan
600 whp in a civic requires a 3rd testicle
How much you build the block depends on how big you want to go.
a b18b is a good cheap boost motor. a simple drag or rev hard kit, tuned, will get you 200 to the wheels easily on 8 psi or so. 200 whp will have you romping on pretty much everything in town. you will own stangs and camaros as long as you can get traction.
if you want to go a little bigger, you need to start thinking custom. and, now, things get espensive. the above will cost you about 3-4 grand. this will cost you 8 easy.
so really, its how fast do you want to go, and how big is your wallet