Now a few months in, I can weigh in on how the DIY Sonos project has gone.
The Good:
Controlling the devices with other devices work well.
Responsive volume change from remote control devices
The Bad:
Once the burner phone screen goes off, the iPad (or other remote) loses connection with it. I have to turn the phone screen back on to get the iPad to reconnect for controlling
Utter (what I'm using for the DIY Echo) has a tendency to screw up playback, and I have to disable Utter
The Unexpected:
If I have a track playing on the living room Plex phone, I can use the iPad to pause that track, then connect the iPad to the kitchen Plex phone and resume. This allows room to room streaming. Sure it's not nearly as swift as Sonos, but I'm doing this on a budget of ~$30 (two phones x $12 each, Plex app for ios and Android ~$5)
