Literally a 2008 Dell netbook would work. Or thin clients. Audio playback, even with convolution and such, isn't that resource intensive unless you're using some ultra high quality resampler.
Acer Aspire one A110 netbook with Atom 230 processor running Volumio & brutefir3 plugin at 192kHz sample rate, 65536 size, streaming 24/352 flac via DLNA is glitch free and has ~55% cpu usage. A significant proportion of that cpu usage is the chromium browser instance that's showing the web interface locally. This was using wired networking with the wireless interface switched off.
Raspberry Pi 3 B running Volumio & brutefir3 plugin with settings as above except for lower filter sample rate confirmed that there are still issues with at least some USB DACs. The Behringer UCA202 is limited to 48kHz output and was glitch free, but at 96kHz with a Focusrite Forte there are occasional faint pops as others have previously reported. The cpu usage was lower than with the netbook above though, so there's power available to run faster or larger filters so long as you stick to i2s interfaces for output.
In short if you want something that behaves like an expensive hifi audio streamer you can use almost any old laptop, or a very cheap used thin client. Convolution will run fine on machines that won't even boot Windows 10. If you want a more general purpose machine that runs Windows and will do other stuff then it's Windows and the other stuff that will decide what sort of spec you need.