Bodine -- It sounds like you've invested some time and money in your system, so I question whether you'd ever be satisfied using whatever soundcard is in your computer as the DAC.
I recently had the Wavelelngth Brick -- a DAC that accepts the usb output of your computer. At $1750, it's not cheap, but it and the iMac G5 together are better than any CD player I've ever had (most recently the Exemplar/Denon 2800 -- a very good model, itself). I only got rid of the Brick to upgrade to the Wavelength Cosecant.
I recently had the Wavelelngth Brick -- a DAC that accepts the usb output of your computer. At $1750, it's not cheap, but it and the iMac G5 together are better than any CD player I've ever had (most recently the Exemplar/Denon 2800 -- a very good model, itself). I only got rid of the Brick to upgrade to the Wavelength Cosecant.