The SteelSeries Siberia v2 7.1 comes with a "7.1 virtual soundcard" which plugs into the usb port. So it won't work with nor does it need another sound card.
Furthermore your onboard sound, the VIA VT2021, has a signal to noise ratio of 110 db. Which is better than most sound cards.
The bottom line is that a sound card won't do you much good(and might make the audio out of your headset worse!). I'd recommend not wasting your money.
Wow.. how stupid could i be?
110db noise ratio? phew.. I'm so lucky that i didnt bought a soundcard alredy ..
To be honest i had very decent positioning with this onboard audo, just thought i can get even more.
Thank you very much! saved me about 100-200 dollar
Now i can spent it on a decent headphone's or something, will probably need an external amp.