I ended up buying 1 Audioengine B-Fi to try out on the first zone before taking the plunge and building it all out at once.

I did look at the sonos port but the top Amazon review where someone states their sonos connect was basically updated to a point of incompatibility convinced me to go with something less managed.

I also saw one person talking about buying 6 Echo dots and tying them to each of the 6 speaker pairs then using the Alexa config to create virtual zones that seemed like a great idea but once again there is quite a bit of negative feedback on the amazon devices (both for privacy and with them defaulting annoying new features to on when deploying an update).

I don't think I will need the per channel volume controls remotely, I can set the levels for each pair so they sound balanced then remotely handle the volume for the entire zone.