Switched power supplies

I would make the suggestion that virtually all general purpose computers will have switch mode power supplies, many folk address the issue of PSU noise at the point of taking the audio out of the PC by using specialist USB audio interfaces or the like - the whole topic is vast and the options many.

My view being that the best that can be done if a dedicated music PC is required is to avoid it being on the same circuit as the rest of the hifi (for the same reason any external audio equipment having an SMPS is also powered from a separate distribution point to the rest of the gear) - I suspect that SMPS feed "noise" back into the mains - not sure how technically correct that is, but do seem to recall being satisfied that it was beneficial to separate the supplies some years ago though most of my SMPS devices are now supplied by linear supplies (computers excepted).

Personally, all my CDs have been stored digitally on my everyday PC on a mirrored raid array and I feed my DAC via a firewire connected audio interface or via coaxial cable from the built-in soundcard (addin soundcard not onboard sound chip).

It is not perhaps the quality I could get with more fooling around, though quite acceptable and serves the convenience requirement very well.   Living in a not over large apartment, cable runs and separate rooms are not an issue for me.

I do think that in the matter of getting good sound from a computer setup, the PC power supply is of relatively little consequence relative to other parts of the chain.

Don't know if any of this will help but perhaps it will.

Edit - just noted from your other post you like MpD - perhaps look up a device called an Auraliti might be just what you are looking for.