What speakers should I get for my gaming computer?

I recently got into pc gaming, and I'm in the market for some speakers. I have limited desk space, so I'm not looking for a full-surround sound system or anything, but I don't want something tiny either.

Right now I have some crap dual speakers and subwoofer, which don't work too terribly well. I like the setup, but the quality is a bit sucky. The volume is fine, but it gets quite tinny higher up and the bass (which is very important too me), leaves a lot to be desired; I want to feel it in my chest.

I'm not really tech savvy when it comes to specs, but for reference I have a fairly new Alienware laptop which is running Windows 7.

Right now my price range is ~$150, but I'm open to suggestions.