Building internals isn't cheap. From your previous posts, I'm assuming you don't have any mechanic experience and there's a good chance you'll be paying somebody to do at least some of the work, right? If so, there's a very good chance you'll break $2000 with the cost of the premade turbo kit and the mechanics labor.
As far as 8 psi not being much - A VERY general ballpark figure (there are many specifics that impact this) is that you'll end up with about 10 horsepower at the crank for each PSI of boost, or 80hp at the crank for 8 psi. You'll probably end up with somewhere around an additional 50whp. An EX has 127 at the crank, stock. You're looking at about a 63% increase in horsepower. While 8psi doesn't sound like a big number, a 63% increase is substantial. Will your car be super fast and ready to eat corvettes? No. Absolutely not. Will you notice a nice gain in power? Yes.
Why do you need more than that? Are you trying to race competitively? Do you want to be the fastest car on the street? What are your goals?