Hobb, welcome. Judging from the diagram, you're too close to the back wall for rear surround speakers to set up a good rear sound field. QS side surrounds in a 5.1 setup, placed on the back wall about where you show the "rears"(preferably 2-3' above ear level and spread as widely as possible)should work well, and there's no need for ceiling speakers to confuse the issue.

M22 mains with, if possible, a vertical M22 or M2 center, would be an excellent setup across the front.

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Enjoy the music, not the equipment.