I have a small man cave in my basement and wanted to add 4 height speakers for Atmos. I also wanted to avoid cutting holes or rigging up anything to hold in-ceiling speakers as the floor joists are exposed and I am not what you would consider a handyman. I ended up going with 4 Polk Audio OWM3's. You can mount them using just 2 screws or you can use a fully articulate mounting bracket such as an OmniMount 10. My Pioneer Elite SC-95 is capable of 7.2.4, but would require having a pre-amp installed for the surround back speakers. Not having one on hand, I tried a 5.2.4 setup instead, installing the OWM's a bit in front and directly above my mains, and slightly behind on the wall for my backs.
I was a bit underwhelmed, but I also didn't like sacrificing my surround backs to add the extra 2 height speakers. I enjoy the separation and location of the sound the surround backs provide.
So I went and adjusted it to a 7.2.2 setup, with a pair of OWM's as MIDDLE heights, and using the remaining 2 OWM's as surround back speakers.
I am much more impressed with this setup. For some reason, I'm able to tell sound is coming from the height speakers better when they are in the middle rather than when there were 4 of them and I had them in front and in back. I think its because my main speakers are a bit overpowering in the small room (SVS Ultra Towers) and my ceiling isnt very high, only about 8 feet, so it was hard to hear the separation between the mains and the front heights. But having moved them towards me a bit, and being in the middle of the room away from the mains allows them to be heard. And I love that I still have my surround backs! Cheap, too. Only about 40$ a piece. They don't need to rock the room, so they do what i need.