I've never heard of it being done. But I'm guessing it will cause some serious conflicts. But neat idea none the less interesting to see if it will work?
Not sure how much $ is for an issue, but why not try to sell the two you have now and buy a 4 channel? After all you may have to pay for the software you are looking for? I just purchased a Soundblaster 5.1 dolby for under $100 and actually the speakers were more than the soundcard. As a total I spent probably $275 on the package plus a cable to run to my home stereo and now I don't even use my PC speakers go figure? Only time I use the PC speakers is for DVD and unless you are watching movies [dvd] with surround you shouldn't even need the 4 channels for music.
But will be curious to see what you find!
