Plenty of threads on this subject; definitely get your sound off the computer via USB (do not use an internal soundcard) - your options are either an external conversion to SPDIF via a device like the Empirical Audio OffRamp, Hag USB, Waveterminal U24 (used), or other similar conversion device. Or you can get a DAC that accepts USB input (does the conversion internally) such as Apogee's MiniDac (USB version), Wavelength (various models), MHDT (available on eBay), or others. Your choices will depend on your budget, but in general the technology is very affordable when compared to state-of-the-art transport/players. Along with the archives here, you may want to check over on AudioAsylum there is a dedicated section for PC Audio that has quite a bit of useful input.
Marco
Marco