I don't own a RSX but any forced induction system (superchargers & turbochargers) will substantial increase the amount of power. They work by shoving and pressuring air into the motor (opposed to just letting air being naturally flow/sucked in). Here's how it kinda goes (from less air to more air).

* Stock Intake: Air naturally flows in
* Aftermarket Bigger Intake (like the Injen the guy above me mentioned): More air naturally flows in
* Forced Induction: Air is pressurized and forced in.

The supercharger runs off a belt off the crankshaft; the turbocharger is spun up off your exhaust gases. There are pros and cons for both of them but it's kinda out of the scope of this post.

You may run into reliability issues when installing a forced induction system on a naturally aspirated motor, basically they weren't designed to take that much pressure. If you boost high, you probably will need new forged pistons, gaskets, cylinder heads, etc... Oh, and a supercharger or turbocharger runs at least a few grand. I know Jackson Racing makes a supercharger for the RSX. I know there are turbochargers for RSX but I forgot who makes it (maybe Greddy?).

http://www.jacksonracing.com/Browse/...&PlateTypeID=1

And for the record, I'm simply tackling this on a theoretical sense. Feel free to correct me if I got something wrong. You should ask someone who has actually installed a turbo or blower for a RSX for more info on it. But yeah, superchargers and turbochargers are the way to go if you want a lot lot more power. A stock RSX Type-S has 200hp, I think. After running a low boost forced induction system, you should start at least 250 and go up as far as you want (until you blow your engine).