One of my best friends has a PC front end that uses multiple LPS, isolation, OCXO USB output cards, battery supplies to run internal SATA drives e.t.c e.t.c
All these things improved the sound and I heard them being implemented step by step. But the biggest improvement, which moved the audio from sounding digital to a real life type naturalness, was the JPlay shutdown mode.
JPlay software for Windows has a special mode that turns off all motherboard functions (including video output and mouse/keyboard controls) in an attempt to minimize all the EMI/RFI created by a computer motherboard design. Essentially it buffers your chosen WAV files directly out of RAM to the output, powering down and minimizing everything else.
It sounds amazing - but the catch is once you set the chosen tracks to listen to (and that is a convoluted process in itself involving pasting exact file name into a text file) you lose all control of the PC. You cannot pause, stop, skip a track or do anything else until you reboot the PC. Its very very non user friendly and impractical.
He set this rig up 10 years ago following advice from the JPlay forums. I expected audiophile manufacturers to have followed this path with dedicated hardware but it was obviously very difficult and has taken longer than expected, with only now the latest streamers from Auralic, Aurender, Lumin e.t.c are using in-house custom CPU processing designs rather than the noisy, off the shelf designs best suited to the PC industry.