So still having this problem, might head to a stereo place or something I guess. But one last shot here? Just to reiterate, everything just sounds like low bitrate sound (i.e. awful). I have changed literally every single component of the setup at some point (motherboard, sound card, receiver, speakers, speaker wire, routed speakers through subwoofer/routed directly to receiver, used different component to aux cables, played from PC and turntable in different inputs to the receiver). I've changed some settings on the computer itself, but any other suggestions on that front might be the most fruitfull. At this point, I have literally no idea what it could be