Multi-Room Audio Suggestions

Hi all,

I just bought a house that came with some built-in speakers throughput and am looking for suggestions on how to proceed with creating a multi-room audio setup.

The house currently has four rooms with speakers hard wired and I'll probably add two more in the future.

I want the ability to use up to three input sources to create dynamic zones across all of the rooms. I like the idea of adding a keypad controller in the rooms, but would also want to control via my phone and the Google Assistant.

From searching around, I've discovered controller + matrix amplifier setups from Casatunes and Control4 that do exactly what I want. There is also, of course, the Sonos option. Plus, some perusing on this site tonight led me to discover Russsound.

My main question is, are there any additional things that I should be researching before I take the next step of focusing on what to buy from those products that I mentioned above?

Also, does anyone have any opinions on how I should create this setup? The Sonos option seems easy but almost...too easy? Also I think a bit more expensive if I were to go beyond three rooms.

Thanks!