Consider running cat6 instead of speaker cable and using Chromecast ultra/active speakers or keeping the amps near the speakers. Streaming audio is super reliable over wired ethernet, so no matter whether you use Chromecast or Sonos it will be solid.
All chromecasts would be wired up via cat6 whatever happens. and there are multiple data points in every room as well.
I have been told in no uncertain terms that I have to minimise the number of little black boxes in every room, hence running everything to a central location.
Consider running cat6 instead of speaker cable and using Chromecast ultra/active speakers or keeping the amps near the speakers. Streaming audio is super reliable over wired ethernet, so no matter whether you use Chromecast or Sonos it will be solid.