OP you are correct that the Anthem MRX 1120 is not a good enough amplifier stage for the Persona 3F.
We have used the Anthem MRX 1120 to power Atmos louspeakers and a seperate power amplifier to power the main, center, and rear surrounds.
One of the most musical multi channel amplifiers is the Audio Control Pantages a 200 watt by 7 Class H a varient of Glass G, that uses two voltage rails to emulate Class A operation without the heat generation.
The other option is receiver to powr all speakers except mains where you use a hign end two channel integrated for music.
Please feel free to contact us we have a lot of experience in this arena.
Dave and Troy
Audio Doctor NJ Paradigm, Anthem, Audio Control, dealers