Raspberry Pi 4 with 4gb ram is allllll you need. Usb output works superbly well, and you can get that setup for under $100 easily. Get an 8gb micro SD for a few $ and spend about 5 minutes of time following a Volumio or Ropieee tutorial. There is no contest. Flawless.
There is also this Raspberry Pi alternative (hat tip @David_Snyder)
But if you don’t have asynchronous usb on your DAC or amp, then you can grab a WiiM mini ($90) or an iFi Zen Stream ($300) for optical or coaxial.
If you don’t have a good DAC or integrated amp with a good DAC then you are going to have to rethink this.