I have been running two RPI 3s (not the +) for a few years now. I have one with a HiFiBerry DAC + Pro and one using an old HRT Music Streamer II+ I have from a previous system. I use one to feed kitchen and patio speakers and the other to feed a little headphone amp at my desk. If I ever add another HAT I will give ALLO a hard look.
I would like to have an RPI 4 now for the added RAM and AC wireless, but not quite worth the money at this time. Don’t suspect the resale market exists.
I have run from the initial Raspbian through Volumio, Ubuntu MATE, and MoOde. Am now back to Raspbian, which I think is Buster. The reason is that the one for the kitchen I added XRDP and the wife can RDP in and listen to her Pandora. You don’t get a browser with Volumio or MoOde. I added Raspotify, which is a Spotify Connect client to both and use them as an endpoint/renderer from the Spotify computer I use for my main system.
Volumio and MoOde both can be used as endpoints for Spotify. They also have a good NAS mapping capability. Raspbian has a version of VLC, but I normally load Clementine to play anything from my NAS.
This are both pretty rudimentary setups, but they do quite a bit for not much.