I had four QS8s - two sides, two rears. Now with two side QS10s, I don't need rears or Atmos.
To be fair, the 7'2" ceiling where your QS10's are located is not ideal for ATMOS anyways where Dolby recommendations specify an optimal range of 7'6" minimum to 12'. It would be hard for you to get optimal sound dispersion of a downward firing in-ceiling M3 to cover viewing positions greater than your sweet spot (i.e. if you have a multiple row seating arrangement or even seating that covers what I imagine is a 24'x25' room (4200 cu ft = 7.16x24x25). You have to admit this is likely an atypical room configuration for home theater where the power of a QS10 does come in quite handy to fill your room.
However, in a more typical rectangular room configuration that is 14-18 feet wide, the QS10's may actually be too close to the listening positions to be fully effective without being overpowering. This is why QS4's can actually be more effective than QS8's for pure home theater use.
This also all boils down to what you actually use your space for. In a dedicated 90%+ movie home theater room, I would definitely recommend that ATMOS is far superior to 5.1. I am simply blow away at how good some of the recordings are. Ready Player One is not a great movie plot/acting wise, but holy cow is the use of ATMOS sound placement technology used well! Mad Max Fury Road is another such title. I really don't care for the movie but really appreciated the work put in by the sound engineer! I have watched it in 5.1, 7.1, and 5.1.2 in comparison tests and ATMOS is noticeably superior. Fantastic Beasts is another such title.
To be honest, my wife and two of my kids simply don't notice or care. My third child shares the same passion as I do for sound so he notices and agrees.
