The PC is easy with that budget. I got an Acer Aspire, put in an SSD 250gb drive and downgraded to windows 7. Final move was to buy Jriver. There went $500.
However, I spent almost as much on a DAC with USB input. Your system will only be as good as the signal coming out of the PC. If you have a desktop, you could install a good soundcard. However, I really don't think there is a soundcard I would buy over my Schiit Bifrost.
The other option is to get an SPIDF adaptor (Music Fidelity V Link) to convert USB to digital and then go into your digital input in your system (if you have one)
However, I spent almost as much on a DAC with USB input. Your system will only be as good as the signal coming out of the PC. If you have a desktop, you could install a good soundcard. However, I really don't think there is a soundcard I would buy over my Schiit Bifrost.
The other option is to get an SPIDF adaptor (Music Fidelity V Link) to convert USB to digital and then go into your digital input in your system (if you have one)