How many rows of seats?
Are there any clearance issues (ie: the speakers infringing on a walkway)?
While mono-pole (ie: direct-firing) are preferred for Atmos configurations, many people continue to have success with bipole speakers. Di-poles are NOT recommended. Bipoles work well when the surround speakers are too close to a person's head.
In any event, if you are thinking about Atmos, I suggest that your bed-layer (7.0) speakers be no more than 1/2-way up the wall. This will give you good separation between your surround and Atmos channels.
As for speakers, the RP-500Ms are all you really need. The RP-250S would work well too, and you will have the enviable all-matching HT layout.