Curious to know how you made this work as I seem to be having the same issue. I have an EA3 controller with analog out connected to amp 1 and digital out connected to amp 2. EA3-HDMI is also connected to amp 2 for on-screen navigation only, not for audio.
When I play Spotify in room 1 (=amp1) and I activate room 2 (=amp 2) based on current_playing_device in room 1 (room 1 selected_media_device = room 2 current_playing_device) then spoitfy starts playing in room 2 as desired.
Now the problem:
When I play TuneIn radio in room 1 and I activate room 2 the same way as described above, SR-260 shows TuneIn as the selected media, but amp 2 is not switched on so there is no sound. If I select listen->tunein room 1 on my remote then amp is activated but not automatically the same way as Spotify follows in room 2.
Idea idea why Spotify does switch the amp 2 on, and TuneIn radio doesn't?