well, a Comptech header will net you about 30 wheel horsepower, so you'd be looking at 300HP (if you have a Type-S) with a simple bolt on. They're quite expensive though...about $1200.
www.comptechusa.com
As always, try to upgrade your suspension with your engine..slightly stiffer shocks and springs that will lower your car slightly as well, and some anti-roll bars for increased stiffness. Add a set of Potenza S-03's, and you're looking at one mean 300HP CL-S
I assume you do have the Type-S if you're looking for more power...is it 6 speed or auto? What color? Congrats on a really great car :thumbup: