The squeezebox from slimdevices.com is worth a look. It doesn't have a USB input port but it does have both Ethernet and WLAN interfaces, which will allow for remote connectivity to your server-based jukebox. It can play a wide variety of digital formats including uncompressed PCM. The S/PDIF output will allow you to bypass the builtin DAC, and use one of your choice.
I don't have personal experience with this device. However, I'd guess that RFI and jitter might be the two main issues.
I don't have personal experience with this device. However, I'd guess that RFI and jitter might be the two main issues.