I use here on PC foobar2000 and there is a free upscaler called SRC. I tried it on Qutest, and when set to resample (not upscale) 384000 I had a feeling it improved something. Since Qutest has that top window where you can see the frequency of the input signal, it was simple for me to check if this works. So many solutions, all going somehow into the same direction, some of them free. This is something basic, but it can upsample to 4x.
But the main problem you have to fix on the PC is the USB connection before any of these resamplers. I will not start a storm of discussions here, just provide a
link.
In my case, an USB card externally powered, improved greatly the quality. As I said before, I use M Scaler also on optical input with an external CD Transport and sometimes compare the same CD from my PC or directly via optical, and there is a difference, almost all the time the CD sounds better.