To ATMOS or not to ATMOS, that is the question you must answer.
If no ATMOS and you want to get into separates, the Outlaw 976 or the Emotiva MC-700 would be high on my list.
If you think ATMOS is in your future, I've been happy with my Onkyo TX-NR686 which has a "claimed" 100wpc (10 more than the Denon?) and I'm running a similar speaker group as you (M22, VP180, QS-4's). The VP180 is a 4ohm beast and the Onkyo is handling it fine (I did add some extra ventilation though to keep it cool). I would think any of the mid-tier+ AVR's from all the suspects would be a good upgrade from the entry-level 2015 Denon model?
Of course, more robust brands with better internal amplification should also be considered. ARCAM, NAD, Rotel, Anthem, etc...
Every now and then I contemplate a full upgrade into separates. Top contenders for me would be the Marantz AV7705, Emotiva RMC-1, Anthem AVM-60, and the Bryston SP-4 (wonder if Axiom owners could get a discount ;-) ).
I'll stay out of the power amp recommendations. Definitely, the ADA's are worthy contenders.
