I honestly wouldn't bother with Atmos. I have added 4 ceiling Atmos speakers to my existing surround system and was not impressed at all.
My room size is similar to yours. My fronts are LS6 and X-Voce, mounted above the TV.
I was using ceiling-mounted compact Infinity satellites for side and surround channels. I have re-purposed the ceiling speakers for Atmos, re-positioning them according to Dolby guidelines. I have also added 2 ear-level X-LSes for Left and Right Surround. This resulted in very little noticeable difference from previous setup even after playing with some additional +db boost to Atmos layer speakers.
I have to admit that my particular setup could be the culprit. I'm already used to hearing surround effects from above, my front channel is too high. Front speakers are also quite tall and the very nature of line array vs point sources might be interfering with Atmos' 3d positional audio. Who knows exactly? Perhaps Danny could explain, but somehow, I get an impression that he hasn't dabbled much with this new marketing gimmick.
I'll let Danny correct me if I'm wrong but AV1/RS are designed to be bounced off the ceiling to produce more diffused, unlocalizable surround effect. This might be the complete opposite of precise object positioning that Atmos is trying to accomplish.
P.S. Some apologies:
1. Danny, if you feel like my post is costing you some business by deterring the sale of 4 extra AV1/RS, please delete this post altogether.
2. Admittedly, I have made a single post of what could or should have been split into several different ones, specifically:
- advice to the Original Poster;
- Danny's opinion on Dolby Atmos;
- problems with Atmos with MY particular setup and possible fixes.