If your ceiling is low (<8 feet) and/or aesthetics are a concern, the M3 in-ceiling is the way to go.

In-wall M3s into the ceiling, and somehow angled towards MLP, would be better.

If you want the absolute best, full-cabinet speakers, somehow mounted to the ceiling and pointed towards MLP are the way to go.

I'm perfectly happy with my 4 in-ceilings, which are far better than the bounced Atmos effect speakers any day of the week.

Axiom M5HP VP160 M3 ADA1000
Anthem MRX 720
SVS SB-3000 (dual)