My room is over 20,000 cu.ft. and although the two would have been enough for us (along with 4000 watts driving 4 seating mounted tactile transducers) I'm not a huge fan of fans.
So if the 2 I have now are any indication ..... I suspect 4 will move enough air to keep us cool this summer ...
Actually I'm also trying to ballance the cosmetics of the system.
I have a 90" Aquos LED TV, with RF-7IIs on each side, and a horizontal cabinet below the TV that houses an RC-64II, with the 12's on each side.
That puts the 7's at +/- 30°.
Then there are two verticle glass door cabinets outside of the 7's, with a pair of RF-82II's for wides.
That leaves a large hole above each of the 12's, below the bottom of the 90" TV, that 2 more 12's will fill nicely.
I'm using RS-62II's for surrounds, all fed from a Onkyo 1010 as a pre-pro for an XPA-5.
I hope to have it all hooked up this coming week.
My wife's getting a bit weary of the mess I've made out of the house.