Good choices for whole-house soundsystems replacing an intercom

My older house is rocking a 1970's era intercom. Every room has a speaker in it, with low voltage power from the central console in the kitchen. I'm looking for a whole house sound system that could replace these speaker-panels in place (10" square), and my fantasy is to do it with low voltage. Probably there will never be a very good low voltage speaker system, so maybe I should give up on that :-) I don't care about intercom usage, that's purely optional. I don't want cameras, either!

Ideas: 1. Sonos speakers 2. Google home 3. Homemade system (or from someone else) that has touch screen panels and speaker in each room. How about large format cell phones, with a speaker?

One solution is put sonos in each room, but it would be nice to have a control panel. Now there are the google home systems. Star trek computer talkins would be fun, but do I want a potential spying device in every room? How about a super advanced system where I roll my own voice recognization (so I could control it better...) that connects to search engines, has a touch screen, and speakers, and connects to whatever streaming system I use.