Well GFX etc. is irrelivant to sound quality ...
To those who think lower power PCs are just as good for recording - for simply recording, yeah - they are. Although its not as simple as that, if your adding a track based effect on a 196kHz channel with a Duron its going to take quite a while Also if your multitrack recording (although your not it still stands) not only does your hard drive have to be upto it, your CPU also has to be upto it.
Active monitors - these maywell be better for what you want although watch out your buying monitors, and not just monitor looking PC speakers Also spend as much as possible as without a flat response - what may sound good mixed on one pair of speakers could sound nasty on another pair. Also unless your a professional studio who can setup them properly - Subwoofers are a big no As they distort the frequency response.