Best music server for the money

Best value for what is needed is any decent PC with adequate USB disk storage for main and backup copies accessed via a network connection.

The server only serves data the same as any client/server computer application. No music is made on or by the server.

The client player device/streamer and its associated DAC and connection is where the music is made and difference in sound quality will occur, so this the place to focus on for good sound quality, assuming the rest of the audio component chain downstream is up to par already.

Agree, the extent one can DIY with a computer is a big factor. If not, buy something with everything needed installed and integrated up front that also offers good customer support. It will likely cost a bit more but be worth it. There is nothing audiophile about a server though, its straight up computer nuts and bolts, so be careful about falling into the traditional audiophile mindset of more expensive means better sound quality, like often may be the case with actual sound making devices like turntables and even CD players or DACs. If done right, a server for music alone need not cost much in any case.