This a very small restaurant with very limited trusted staff, not too worried about users damaging anything.

The 3/3 speakers are sort of scattered around the ceiling and surprisingly sounds pretty good. The room is small enough it just works. No matter where you sit in the room you are still close enough to either a right or left channel it isnt awkward feeling.

I would love to be able to run the whole setup mono but, the Onkyo only gives you that option on FM which we probably won't use much if ever.

Have not really played with Sonos much.

I have Denon Heos at home though and had thought about using something like that. The "app" based things seam quirky/glitchy that I have played with, although it may be my network is not solid.

I am an overqualified diy'er at this stage of the game...

At our other restaurant we use Rockbot, sort of a virtual juke box that customers can buy songs if they like on their smart devices, for our music streaming service and that takes care of the music police issues there... And we can control what plays when and limit or expand content on the fly with smart phone management apps or from a pc based online management console page. Sometimes they stream some pretty obscure music but we have control of genre/explicit limitations, etc. We have a much larger system I cobbled together that rocks the house. 9 zones, 36 speakers and and multiple subs throughout. I used all old Rane controls & QSC amps and ceiling speakers and inceiling subs in the bar and one day the regional sales rep from QSC happen to have a meal in our bar on a very busy day and asked for the owner to ask who the contractor was that installed our system. I told him it was me and that everything was found used on EBay... He stated it was one of the better systems he had heard spec'd with his line! I have an in wall source selector and volume control in the bar only. Everything else is in a 42u rack locked away from most of the staff. It is a, set it and forget it, system other than in the bar, they can switch source for games on tv and such and turn the volume up and down when it's busy.