I just upgraded from an Anthem AVM 50 pure processor with my Luxman and 3 outboard monoblocks to MRX 540 receiver. I'm using built in for center/surround and outputting line level to my Luxman.
The cost of a new AVM processor is pretty steep so I ended up compromising.
My honest advice is that the jump in sound quality and, with tweaking, the ARC you are much better off going with MRX and getting all the modern HDMI/audio goodies than you would be sticking with an AVM 60.
The negatives are that there is no built in Roon support and who knows if it ever really arrives, and no USB input either.
Seriously, it is not even close to a debate for me anymore. If I could not afford the latest processor I'd jump on a new MRX long before I got a previous generation processor.