Hi @barritia.
Thanks for the update here, my apologies for the delayed response.
To better understand your system/setup, kindly submit a diagnostic report through the Sonos app, and reply with the confirmation number.
To clarify, the Sub is the only speaker ‘bonded’ on the Arc as a home theater but the Dolby Atmos is just from the Arc, while the Amp is set or named as another ‘room’, and in order to play the same sound on 2 ‘rooms’, they need to be ‘grouped’ together. If the Amp is added or bonded to Arc, it will work as surrounds to enhance the sound but it will not get the Dolby Atmos signal from the Arc, the same thing if the Amp is ‘grouped’ with the Arc to play TV audio, Arc will not send a Dolby Atmos signal to Amp but you will get the most out of the Amp which is ‘stereo’.
Most S2 compatible players support 24 bit audio. For the select few that don’t, they will automatically downmix any 24-bit audio to 16-bit when streaming. If your grouped speakers do not support 24-bit audio, they will automatically downmix to 16-bit audio. Speakers that support 24-bit audio will stream 24 bit when grouped. At this time 24-bit support is limited to local playback from Music Library, NAS shares, or playing music from your Android phone or tablet.
If you have any other questions or concerns, don’t hesitate to reach out, we’re always here to help.