i imagine you are talking rwhp. So with that said, you could port the heads, bigger valves, port the intakes, and cam. That should get you but 170hp at the wheels. Either route you go you will need a dyno tune and i would def recommend bigger injectors.
if you want constant power then go with the heads and slowly build the motor. Nitrous is fun, but refilling the bottle gets expensive in the long run. You could always just get a supercharger, i saw a procharger for sale somewhere for a good price. Running low boost you could get 200rwhp on a stock motor.