Hello and thank you for the question. Here's the thing- with ONE Ipod you will be able to only stream ONE source of music to the Zones. For each Zone to be able to playback different sources- each Zone will need ONE Sonos "Bridge" per Zone (at $350 each x 12). The only other solution is to purchase a Home Theater receiver with a Main and Zone 2 Output- which will give you TWO sources, in addition to using the Ipod through "Sonos" which would be your 3 rd source.
So in order to have 12 independent Zones- you need 12 independent "Sources"- or you can have ONE Sonos connect to ALL Zones- and they will all stream the same music.
I'm afraid there is no simple way around that, as the music streaming devices only stream ONE source at a time.
For 12 channel Amps, the one at the link below is by far the best for the money- providing 60 watts per channel RMS, and stability into lower impedance loads for the extra 6 speakers that are sharing the 12 zones (18 speakers-12 zones= 6 extra speakers).
Then Sonos is still your best option (actually the only option), to be able to use ONE Ipod and stream to many different Sonos boxes- with each one obtaining it's own IP address and therefore being able to playback a different source than the other Sonos boxes (Sonos Connect):
Amazon link (ONE for each SOURCE you want to stream):
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