Hi @tom22
The way I see it, you have 2 likely options - connect a Sonos Amp to the speakers above the sofa and connect a different (one) Sonos Amp to the other four speakers (Kitchen and above TV), as you are thinking. You’d have surround sound normally, and should you want TV audio piped through to the Kitchen (for a Football game, for example), you could group the Kitchen/Above-TV Amp with the Beam so it plays TV audio, while muting the Beam and other Amp to ensure they do not play out of sync (I should clarify - the Beam+Amp would be in sync with the TV picture, but as the other Amp would cover the large space better, it would feel like the Beam is out of sync with it, while it is actually the separate Amp out of sync with the Beam). Music can also be piped to all speakers, but you need not worry about synchronisation with music sources. I think this is what you are currently thinking, and it would be workable. Please feel free to ask further questions if you want to be sure of anything in particular.
Or, connect a Sonos Amp to whichever 4 speakers you’d like configured as a room (and the other 2 to another Amp, if you like), and have some Era 100/Era 300 speakers performing surround duties for the Beam - as the Beam (Gen 2) can support Atmos, it can make use of the extra drivers in the All-in-One Era surrounds. This will result in better Atmos surround sound rendering, though I understand that additional speakers might have a lower spouse-approval rating (and power sockets would also be needed)! The price will definitely be higher, however.
From how you worded your initial post, I think the former would be more to your liking, but the other options are there. If you feel that you may want to upgrade to the Arc Ultra sometime in the future, I’d recommend going with the Era 300s now to maximise your future upgrade potential (while minimising the total upgrade cost).
I hope this helps.