IIRC according to Tom's Hardware, the nForce ("XBox") chipset has pretty good sound. And, I'm sure they'll support W2K.
Frankly, I don't think you're going to see much competition in high end sound cards because it's not a growing market (and good sound on motherboards such as the nForce has the potential to really hurt CL), and there isn't a huge market for really good sound cards.
Tony