hp/$ turbo is the best way on stock internals w/o pulling the motor and can be done in a long weekend from start to finish for most people.

nitrous is the cheapest initially hp/$, but you need to take into account that it's not always there on demand and refills over time amount up.

for 200ish whp go moderately sized turbo, tuned and ride out. it sounds more like you want a street car anyway and not a highway killer or strip car, so you can acheive what you're looking to do w/o taking out loans, etc.