IMHO you really don't need to spend much on a PC
If you want to save money, like me I recommend a PC like this
https://www.amazon.co.uk/dp/B08GHCD...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
< £200.
I bought a Beelink S1 (no longer available) and it is perfectly adequate.
If you do this I would recommend sticking with windows on the device as putting Linux on it is a faff. I have had a PC like this running for 2 years without issue. It replaced a vortexbox and is much smaller.
If you want to use it as a music server, i.e. with all your files on it then you will need to install a 2.5 inch drive. There are 2 types of drive Solid state which are faster dead silent but more expensive or mechanical which are not quite silent but cheaper. Do not get a mechanical Hard drive > 2 GB as it won't fit in the box. If you need a larger size then use an external USB drive. There are some no name chinese Solid State drives that are affordable now at 2 TB. e.g.
https://www.amazon.co.uk/TCSUNBOW-S...nternal+ssd&qid=1604073687&s=computers&sr=1-8
It will be absolutely silent.
I run the PC without a monitor and have Squeezebox server installed as a service along with plex media server for videos etc. Running the application as a service means that it will re-start automatically if the server is restarted, without having to log in. I have set the server to reboot once a week to pickup windows updates. Squeezebox server is free and is easy to install on windows there is some effort to get it running as a service and occasionally it will bugger up e.g. the last windows update meant I had to upgrade the SB server version.
I use raspberry pi with picoreplayer installed for playback in my lounge, this allows me to have the pc in the study and the Pi's connected to my main stereo in the lounge. But this kind of setup is over-kill if you are just using the player in one room.
I also have squeezelite-X installed on the pc and run it with a monitor and output sound via my Motu USB DAC.
For remote control I either use the web interface with material skin enabled or orange squeeze on my phone.
You can also install Roon or Jriver if you choose or any number of DLNA services instead of Squeezebox server.