Am I correct in that I count 5 zones?

I have installed many Casatunes systems and people love them. I have this one on my house:

[Link: casatunes.com]

It has 4 analogue zone outputs and one digital optical zone output, for a total of 5. You could run the optical into your Onkyo and because it's network capable, Casatunes will turn it on and off when called for using IP control. The other 4 zones you use amps of whatever configuration meets your impedance and power needs.

It also has wireless AirPlay zones which can steam to any AirPlay device including stand alone AirPlay speakers.

It has a built in hard drive to store music on and connects to all of the usual on line streaming and Internet radio sources.

Control is trough iOS app, android app, keypad, or web browser on a computer.

And, it's all in one small box.

Great support too.

Craig.