Very good points. I am starting to swing towards grabbing an AVR390, despite what I've said about integrated amps. As long as that eARC splitter does the job, it would probably be my preferred option to have one (very attractive) box. Had two Arcam AVR's in the past and was very happy with both, so as long as I can mitigate the HDMI obsolescence issues, I'd be happy.I was using a Denon 4400 plus Musical Fidelity M3i directly before getting my Arcam AVR550.
I much prefer the Arcam, it sounds as good as the MF for music and better than the Denon for movies. It's also a neater and more convenient set-up for the family lounge.
Dirac does a much better job in my room than Audyssey did, although I use a very light touch on room correction because I like how my system sounds without it. But, Dirac does do some magic for dialogue, so I use it on my front three speakers for films / TV and not at all for music.
Whichever way you go, you do need to factor in something else to use as your music source, such as a cd player / DAC / streamer. The MF amp is analogue only, and, to me, the Arcam sounds best in stereo direct mode when being fed an analogue signal.
Realise your AVR550 is a step up from the 390, but in my small room the 390 should be enough power-wise, and I've never heard much bad said about sound quality. What HiFi suggested it could do with a bit more punch but I'm not convinced by that and I'm a bit volume constrained anyway.