I don't know hardly anuything about soundcards, since im a console gamer, but from what I understand, those headphones would probably sound pretty damned good on your standard one.
I use the Fischer Audio FA-011's for PC gaming when I play stuff like starcraft and League of Legends, and I find that they have just as good if not better positioning and soundstage as my ax720's do on console, and sound better quality as well..
I have a very basic sound card that came with my computer, by the way
However, I noticed that they dont sound very good through my tritton decoder box on console, which is weird, but I bought them for music enjoyment anyway, and they do wonderfully for that
The fact that they do so well for PC gaming was just an added bonus to an already amazing purchase
I don't have a sound card at all, just integrated mobo. Xonar comes with Dolby Headphone, and I really want to experience this. I guess ill just do it!