I like headphones mainly because I can blase music, or the game im playing. Headphones are a huge advantage playing games, if you have it at a little bit more then a reasonable volume, you can hear the enemy very easily. IE in cs often people will call me a n00b h4x045 because i could hear them running away from me down a hall rather then towards me and shot them. Its totally 1337.
Those headphones are amazing, they use them in my schools radio production class, and are of amazing sound quality. Im using them right now listening to rammstein, and it plays better then the regular stereo in my house.
Plus thats a pretty good price on them. It'll be cheaper then that sound card, and I think the sound quality will be on par, or heck may sound better then that card. I have always loved headphones.
I say screw the sound card, and just get headphones, sound always seems to better coming from headphones to me.