I don't think I followed a specific guide. I'm using the HifiBerry Amp2 amplifier with the Pis. The house I moved into had Bose in-wall speakers in a couple of rooms and I added some in-ceiling speakers and a couple of outdoor speakers. Most of the speaker wires are routed down to the basement, so I can have all the Pis connected right to the switch via Ethernet.

Running speaker cable is by far the hardest thing about this. You could also connect the Pis via Wi-fi; I haven't tried that but it is supposed to work pretty well.

On the software end, it's pretty simple. PiCorePlayer is just an image you burn to an SD card and boot up on the Pis. I run LMS in a docker container. As long as the PiCorePlayer instances and LMS are all on the same subnet, they will auto-discover each other. If they're not, it's just a matter of configuring the LMS server URL on the PiCorePlayers.

LMS configuration is also pretty simple... you point it at your music folder and it will scan and index your MP3s and other audio files. It has plugins for Spotify, Tidal, Youtube, and some other apps. You can control it via browser, or there are Android and iOS mobile apps.

Once you buy the Pis, amps, power supplies, and cases, you are looking at probably $140 or so per zone... so it's not entirely cheap, but I think it's cheaper than Sonos or other pre-built systems. It sounds great and the different Pis sync very well. I don't hear any sync issues walking from zone to zone.