I don't see either a 12V trigger in or out on th e NR1200, so you don't have a direct method. There might be work around. You might be able to use two smart outlets and turn both on with a programmed routine. (i.e. with Amazon Alexa outlets... create routines for "Stereo On" and "Stereo Off".) The key is if the power buttons for NR1200 and A-300 are a hard on/off or soft buttons. If they are hard on/off, it would work.
Just an idea.