Hmm, you need to be prepared to spend a lot if you want a fair increase in power. Last year I had Schrick 268 cams, TSR 4-1 manifold, polish & ported head, Pipercross vector induction kit & custom cold air feed, decat, stainless exhaust, and a Stealth Racing remap. It's making 182bhp now, but I've spent well over £2k on it (and most of the major engine bits I got second hand anyway).
Having said all that, I like the way the car drives so I'm a happy bunny.
Beyond that you are into the territory of throttle bodies like Dinky Dave, F2 Stu, Rob T and some of the others. That should get you the right side of 200bhp but again, be prepared to spend.