I think Mesch has given you very good advice. In digital playback the clock is of paramount importance to reduce jitter. A computer is an electrically noisy environment and generally a bad one for a precision clock. A USB-to-S/PDIF converter with asynch USB (probably they all are) will have a precision clock housed in a more conducive environment and the asynch USB will have the computer clock slaved to that of the converter.
This will likely be the biggest bang for buck improvement. Going to higher resolution audio might be second. If you were to go with CD quality then the choice of playback software would be significant too, and the computer itself.
This will likely be the biggest bang for buck improvement. Going to higher resolution audio might be second. If you were to go with CD quality then the choice of playback software would be significant too, and the computer itself.