Hey guys, thanks for these comments, I started to dig in the 40ish pages !

very interesting! Regarding the 4 Ohms question, I've spotted a comment :"
But Gene, thousands of people, and I have connected more than 5 speakers (many people connect 11 speakers, I connect 9 speakers) to this amp in a large room playing loud sound. Many people have connected 7 speakers (that dip down 4 ohms) to the Yamaha A1080 without any kind of issues."
So in "real" life, may be less of an issue.
But it's very interesting that you have the 1080 and still vote for the Denon. I saw also all the debate around Audissey who seems to win.
Also read that the Denon App was indeed not great at all.
agree with you regarding the AI feature, listening to the presentation of this by a Yamaha product reps, I wasn't convinced that it would drives consistent result (like the DSP from what I read...)
Damnit, not an easy choice! best would be to have and test them both

but not really feasible around here.
wonder if any happy Denon 3600 owner could comment on the stability of the wireless connection/ airplay, etc.