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Home Audio Neophyte questions

Apologies for the basic questions. I'm trying to determine what I really need without overspending on equipment. I want to set up my family room for surround sound, speakers currently set up for 5.1. Additionally, I have 4 audio "zones" (speaker pairs) around the house (outside, living/dining room, kitchen, master BR). In the audio areas, I want to be able to listen to independently selected sources (ipod, XM, radio). I currently have the speakers set up with volume controls at each zone.

I am trying to work out the receiver set up I will need to allow me to do above. I expect I will need an receiver dedicated to the surround sound setup. My question is basically how do I extend or add to this to get additional audio sources set up to independent audio zones that can choose what it wants to source.
Thank you.