I don't get what your concern is. If you're using a PCI sound card there is no need to worry about the onboard sound on the GT 220. But yeah there is no SPDIF passthrough to the video card they placed an integrated sound card on the graphics instead. Does your sound system require HDMI or something? Why not just use the SPDIF out of the sound card?
If you really really
want your SPDIF audio from your PCI soundcard over HDMI you'd have to buy something like this http://www.buy.com/prod/dvi-audio-sp...208047492.html
which is kind of a waste really.