You damaged the amps, because you have not heard of ohm's law. A speaker needs to see a narrow range of impedance. For a system like yours it needs to see as close as possible to 8 ohms on each channel. I do not know how you wired those speakers, but without impedance matching volume controls which contain auto transformers the impedance is almost certainly close to a short circuit. So if you take two 8 ohm speakers and wire them in parallel, you have four ohms. If you put four in parallel then you will have two ohms. When you get below 4 ohms for sure, then the load will be catastrophicly low. This is because as you drop the impedance the current goes up as V = IR. That is ohm's law. So the current through the output transistor was too high. This caused them to overheat and melt down, causing them to become a short circuit. The result is what you experienced twice. Shure these receivers have protection, but if you run them over a period in a damaging condition you will defeat it, which you did. Your warranty is void now.
I suspect at your level of knowledge, which would appear to be minimal, that you need a professional installer. This explains
impedance matching volume controls.
This is an example of an
impedance matching volume control.
However with a system as complex as yours driving it from a receiver is less than ideal and probably asking for trouble. There are a couple of better ways of going about it. One is to buy a receiver that has preouts, or use a pre/pro, and then drive each section of speakers from a separate channel of a
distribution amp.
Another way to do it, which is the pro way to do it with that many speakers is with a professional PA 70 volt amp. These amps are designed for powering multiple speakers from long wire runs. It requires attaching a balancing transformer to each speaker. The transformers have taps on them marked in watts and the sum of the wattage on the taps, must equal the power of the amplifier. This balances the impedance.
Lastly the way you have gone about this is dated. If you must have whole house audio packed full of ceiling or other speakers, then there are systems that add a lot of features and novel connectivity now. An example would be the
Sonance system.
Unfortunately the unvarnished truth is that you have barged ahead and installed a complex system with no foundation of knowledge as to how to design, spec. and install it. This predictably has produced a catastrophic result as would be predicted.
So now this will cost you far more money, than consulting a knowledgeable and expert professional in the first place.