Hmm, that's gotta be a first. Never seen anyone suggest a DIY Soundcard. Honestly, I think it would be soooooo not worth it. The hardware part of it is one thing, but then there's writing the driver, which teams of code writers take months, years, and sometimes never do get it right. I'm not saying it couldn't be done, but it would be a big, big project that would require a major investment of your time and energy, and probably as much money as just buying one of the many good soundcards available without the headaches.
RD