Let me list out what I think you are saying you want and how I would recommend setting it up.
You want a receiver that will allow you to play a variety of sources (CD, Ipod, radio, etc.) through 3 sets of selectable speakers. You do not need/want independent source control for each set of speakers, just the ability to switch a set on or off.
Receivers do not have 3 sets of speaker posts that work like an A/B/C type of set up so you need a speaker selector box like the one I linked. Now in order to not overload your amp you need one that will match the impedance so it loads the receiver like a standard 8ohm pair.
So you will connect your sources to the receiver and run a pair of speaker wires from the main left right out to the left/right inputs on the speaker selector. Then run each set of speaker wires from the box to the speakers in each zone. Now you will control the volume for the entire system through the receiver and control which source (cd, ipod etc.) through the receiver and use the selector to control which speakers are playing.
Let me know if that is what you are thinking you want or if I am way off.