Oh my! Probably, a long time ago, an electrician installed the system based on something seen in a restaurant. I can imagine an original 70V something driving the system. Later, someone “improved” the system by adding matching transformers and the Pioneer.

Are these restaurant grade speakers or something better?

I don’t know your budget constraints, but you could pull out a few rooms using Sonos AMP’s, here’n there. I’ve put Connect:amp’s in closets above ceiling speakers in impossible to wire homes.