If you're just wanting to run 4 speaker surround, that shouldn't be a problem, unless you're sound card is using the L/R surround output line as the SPDIF out, too. Even then, some cards would let you use the SPDIF out as your rear speaker signal which I believe you could run with an analog out for the front channels. Another option would be to just run stereo out via your SPDIF line for the games, and get your preamp to do DPLII on them. If you can force Dolbly Surround output from your sound card, this works even better. Still not the same as intentional discrete channels, but still very pleasant.
Kensai
Kensai