My HT/Rec room is 31ft x 30ft x 9ft ceilings and I owned 60's and a 500 for years with no problems. I currently have 80's and a 600, but I think you would be fine if you decide to go cheaper.
The 500 and 600 are very close in performance, as are the 60's and 80's. For the difference in cost between 60's and 80's, you might want to go with 80's. They will give you a little lower bass performance and with dual midrange and tweeters are a little more detailed. But the 60's are fabulous speakers as well.
Keep in mind if you order form Axioms Factory Outlet you save 10% plus another 5% if you buy 5 or more items.
Don't worry about the open areas to the right. In my situation my right qs8 is open to the pool/bar area, and the rear Qs8's are open to the walkout area, no problem.
One concern is it appears you might want to move your left/right surrounds further forward a bit if possible.
