I guess you haven't moved forward yet Ano.
I used the in-wall VCs in my house for a couple years, with zone 2 of my AVR, before adding KPs. Quite functional, though I really wanted multiple sources. That was my main impetus for revising to KPs.
Many AVRs are networked these days, controllable from an app. I think a Sonos Connect:AMP may work as a single device for all the speakers, if you want just background music. Might be worth a try. If the amp is too weak you could then use any old AVR as an amp for it (if Sonos Connect:AMP has line level outputs, unsure).
Both Nuvo and Russound offer whole house audio systems that can be app controlled.