you're actually just below the price cut-off for any real engine that would make any huge difference. The stock motor that comes in the NTC3 is a 1hp Thunder Tiger.
Properly set up and with a CVEC pipe on it, you can compete with some of the higher-end engines.
Anyway, it's my philosophy that if I'm just a bit short on cash of the part that I want, but there's something "nearly" as good that I can afford now... I save the extra few weeks or months and get the one that I want instead of buying what's kinda good at the moment and kicking myself later for it.
When you do get a new motor, if all out power is what you're looking for. The OFNA, or OS .12s with the Slide Carb and Turbo Head can crank out up to 1.6hp and you'd be looking to spend nearly $230 for those.