The center channel speaker should be above or below the center of the TV screen, the left and right channel speakers to the left/right of the TV which all look easy to do from your diagram. The rear should be slightly above and behind your head when sitting. But for that room ceiling or wall speakers as close to optimum as possible could work. It looks like you could get away with a 5.1 set up easy enough to fill the room.

02AN's set up diagram looks good.

Your choice of Yamaha is fine. They seem to be reliable and several here use them. I like Onkyo a bit more feeling the amp section is better but that's merely my opinion. Depending on what models you compare I believe the Yamaha gives more HDMI inputs.

I personally have not heard Energy but they have a good rep. You might also look at entry B&W or Paradigm but those could put you over what you are spending now.