To gain 100whp on a N/A honda engine (B or H series) will take a fully built engine(head and block), super high compression (can we say race gas, no gas station stops anymore) cams that will be unstreetable, and a tuning genious. Not if you are serious about having 300-400hp, go with forced induction and save yourself a few grand in parts and in fuel.
The motor you have now is more then capable of reaching your goals with a little bit of boost (assuming you have a b-series in there now)..

Oh I shall add that you will need high quality parts, for a header that actually produces some power expect to pay about $1,200 + and your stock intake manifold won't do either expect another $500 for a new one along with a t/b.
This car would not be cheap or street legal.