I"m shooting for 300WHP with my Turbo L6. It's probably a bit overkill for what my car is mainly used for. My main motivation is keeping up with my friends with F-Body/LSX cars. On our cruises we go on, my 78 is just about right where I'm at right now. [L28>T @ 10 psi] I would imagine I have about 200-220RWHP.
I didn't even touch power mods before the car was reliable and had a decent suspension on it. [Poly bushing, tokico red springs, HP blue struts, ST front sway] Get to know the car and make sure it handles well. Like the guys are saying, 200WHP is "just right" for most street applications, it's just the speed junky in us that wants more.