As an alternative, you might consider getting this:
Sennheiser puts out a gamer designed circumaural headset that has a built-in USB connector with built-in sound-card with 360 degree sound. The reviews for this headset go from very good to great.
With this buy you get both your speakers and soundcard and microphone with one purchase. And the quality is very high and its good if you want to keep it quiet when you're gaming. AND later - you can then purchase a real high-end sound card (and the X-Fi Platinum is really good) and plug the Sennheisers in for really top notch sound. So you can start with the USB - keeping your costs low for now and upgrade later.
With Sennheiser's 3-D 360 surround sound - you'll be hearing stuff you never heard before from your games- assuming that's what you're building your rig for - and the 360 headsets really give a immersive feel to your gaming that you don't necessarily get with outside speakers.