EasyRaider,
Don't be discouraged. You can indeed get VERY good sound from a PC. You need to start with a solid sound card. The top two in the market that are reasonably priced are the Lynx L22 and RME Digi96/8 PAD.
These cards are made with the noisy PC environment in mind and so are pretty well shielded from EMI/RFI. However, using Stillpoints ERS (EMI/RFI absorbing cloth) still makes significant improvements.
I have the Lynx and it is excellent, but supposedly the RME is almost as good for much less money. I do not know how well they will drive a pair of headphones directly, and you might be better off using an external headphone amplifier. But as they are pro audio the outputs are very 'hot' (high voltage) to drive long runs of cable.... note though that they do not have the usual 1/8" connectors. The Lynx has XLR outputs only on a breakout cable while the RME I believe has 1/4" connectors...
James
Best shielded, most stable (quiet) PSU with active PFC
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