It is not any better than the integrated soundcard. The only good thing about the usb-soundcard is that you can save the volume level and stuff like that directly to it.
But since siberia v2's do well without soundcard, its up to you, and preferably if you are visiting LANs then it might be useful thing but other than that it is really up to you.
Im just asking if its anybetter than the one without soundcard Im only using them headphones at home with my own computer I wont visit any lans. If the soundcard dosen't make them headphones better I will get normal ones but If theres big sound difference with the usb soundcard I will.