We started our computer-based builds years ago by using of-the-shelf hardware: one of the first compact audio servers we offered was based on Intel NUC.
Another hardware platform we found appropriate for our low-powered servers were various "thin client" computers - this one was made by HP.
This was our "top class" audio server. Built-in large capacity hard disk for music storage and a slot-loading DVD drive for automatic audio CD ripping. With several configurations possible, including IR remote control.
However, we wanted to create our own small, high quality audio server, and soon started using Raspberry Pi for our builds: here is an early prototype, plus some early variants of our amps.
Here is the "de luxe" variant of the server - with LCD screen and an IR remote control.
Another development: monoblock Class D amplifiers (2x60W) with a tube preamplifier.
And another custom variant, with a slightly different amplifier enclosure design (top).