Hi @UnifiOOS
Welcome to the Sonos Community!
My initial thought is “can you move the in-ceiling speakers?” You will want to have both of your surround speakers behind you as you watch the TV. If you can’t move them, I’d recommend getting a pair of One SLs to use as surrounds instead (or move the sofa/TV). If you were to use an Amp for surrounds, it will need to be kept within 5GHz WiFi range of the Arc so locating it in a media room may not work as intended unless you connect both the Amp and Arc to ethernet.
As for your zones, yes - an Amp for each zone is what you’d need. Please note, however, that the only type of speakers you can connect 6 of to a Sonos Amp is Sonance Architectural speakers. For other 8 Ohm speakers, Amp only supports 2 pairs of speakers.
Please also note that 5.1 audio is meant to be presented in that exactly that way - I don’t recommend connecting more than 2 speakers to an Amp being used for surround sound duties, though it would work. Perhaps not as intended, however - it’s the rear channels that would be duplicated, so you’re not necessarily going to be able to follow dialogue in the Kitchen if you do this. You can group other rooms (separate devices) in with your Arc for playing TV audio, but it is delayed slightly and if you can hear the original sound coming from the Arc at the same time, it’s just going to sound like an echo.
Music playback will not be a problem - listen in one room or many, to one stream or many.
As for how all the devices work together, Arc receives the stream from the TV via HDMI-ARC or eARC and decodes it. The Arc will play 3.0.2 (L, R, Centre and 2x Height), will distribute the rear channels to a pair of One SLs (for example) or an Amp via a direct, low-latency 5GHz link, and will send the remaining .1 channel to the Sub in a similar fashion. The low-latency links mean that the sound stays in sync with the picture on the screen. When sharing the TV audio to other rooms, however, the signal must pass via the router over a slower 2.4GHz connection and therefore a delay is typically introduced. Music playback, on the other hand, is prebuffered and the system can coordinate playback so that all rooms are in perfect sync with each other.
I can’t really comment on Siri integration (there’s nothing official), but Alexa can be installed on Arc, as can our own Sonos Voice Control (and both can be installed at the same time on the same device).
I hope this helps, and is clear - if you need any clarification, please ask.
