Where there’s a will, there’s a way(though, perhaps, NOT the best for audio apps). If I wanted to trigger a power source, I’d find a 12V coiled relay, with whatever voltage/amperage-rated contacts needed and wire up a distribution box(outlets). Power cord’s hot, to one side of the the relay’s contacts/outlet hots, on the other. Then, whatever configuration of cord needed, from the relay coil terminals, to the 12V trigger connection. The same could work, installed inside each amp, if you’re adventurous. Of course, then you’d have another EMI source(an electromagnet), INSIDE each amp.