My Dad just did something similar. He had an Anthem AV receiver and 5 Sonus Faber speakers.
Out of the blue he said " I always wanted a McIntosh" I said "Do it ! "
He picked up a new McIntosh MA8950. I set it up with the Passthrough that I am assuming the 12000 has like the 8950 and 9550. It is slick. You need to wire a trigger to the Mac from the Anthem trigger out. When you do and select the input you have the AVM left and right front connected to it turns on the Mac and puts it in bypass. You are only using it’s amp section. Then when you power off the AVM the Mac returns to its previous state or to its last input. Or off if you used bypass last. Its really slick and allows seamless integration of stereo and HT
He kept the center and surrounds but upgraded the mains to Sonus Faber Electa Amator III. It is a killer setup with hifi and video sources.