Mario, it really sounds like you are putting too much effort and resources into this problem. Why does it matter if all of these zones come on at the same time? If no one is in that zone to hear it, does it really make a sound?

Grab a surplus receiver with a 7.1 channel analogue input. Split the signal and create a poor mans 3 zone amp (more if you can mono the signal). After you've split the signal then turn each zone on using a relay controlled by the PIR. Set the run time with something like this:

[Link: ebay.ca]

12V LED Digital Programmable Timer Relay Switch Latching Self-lock Module Board

Craig

You have to have an old receiver laying around somewhere pulled out of a job? Hell I have a sherwood newcastle I yanked out because the HDMI board kicked the bucket, Was just going to throw it out or use it for some garage speakers!

Just tie the speakers together and Bam! Ohm load may be wonky but this is your house, you can do it! :P

Love the ingenuity guys.

Thanks for ideas.