Good information. I'm currently using some Google cast enabled speakers and a chromecast audio. It does the job but doesn't have as much flexibility.The HEOS app can stream audio to up to 32 HEOS speakers (ie. 32 independent zones). You can group up to 16 of them for whole house audio passing the same source or pass a total of 8 independent sources to the lot of speakers. You can also group 2 of the same model speakers (eg. I have two HEOS 3 in my office) to form a stereo L/R pair.
This is what I was wondering. I couldn't quite gather that for sure from the manual. I'll likely just stick with my Google cast setup for now unless I can find someone to buy my old soundbar and Google cast enabled speakers.Note however, that the AVR (main/Zone 2/Zone 3) is considered one speaker so you would only be able to pass one source to the AVR; however, you can group the AVR with other HEOS speakers (under that 32 max speaker limitation).