Patching from the out of one sound card into some card on another system probably would fail due to feedback and other problems. Sdound cards offer digital inputs and putputs for devices like stereo receivers and feeding audio in from camcorders and other small external devices. For gaming the two brands looked at now are Creative and Diamond for popularity and sound quality there.
The Creative XtremeGamer can be looked over at
http://www.newegg.com/Product/Produc...82E16829102006
M-Audio is another brand with digitial and optical output on some of their models.
http://www.newegg.com/Product/Produc...82E16829121006
It will also depend on where you plan to order from.