I should clarify. The Anthem continuously produces a 12V trigger signal when on, and it turns off when the Pre-Pro turns off. The Anthem isn't the issue, it's the Proceed amps. They are the ones that require the odd protocol for turning on and off. As far as I know, all modern gear just sends out 12V over it's trigger outputs when on. The Anthem is even versatile enough to include 3 trigger outputs, with 2 different current draws.

I thought about an RC circuit like you suggested, but instead just ran the capacitor to ground and it flips the relay again when it is sufficiently discharged. Same idea as you are suggesting, just simpler for this application.  Separate on/off RC circuits each with a relay one attached to the NO and one the the NC would do the same thing, just would take a few more parts. 1000ufd decays in a little less than 1 second, so the pulse is of sufficient length for the Proceeds circuitry.

I'm just amazed that I had to go through the effort for the Proceeds.  What was Levinson thinking?

BTW, I may have screwed up the below schematic. I suck at drawing them, but the circuit works, which is all that really matters.