I am using a 6500 UB, and a Carada 110" 1.78:1 screen. Very happy with all of it, other than Epsons rebate program
. Performance wise the product is great. Movie theatres are useless to me now, unless I just can't wait for the movie to hit video.
I currently played a lot with QS8 speakers placement and I find your configuration to be wrong. Don't know if you're willing to try something. Keep your couch at the same distance but center it in your room to have the same distance on each side.
Move them 18" each in front of your back couch
I'm not suggesting that you move the speakers permanently, put them temporary on something to try out.
see the picture, when I listen to a movie, I move the couch beside the lamp near the wall. Between the side QS8 and the back QS8. I could live hapilly without the ones in the back but the ones on the side are really in the sweet spot.
Since you room is dedicated to your home theater, I would suggest moving your couches. Put your couches one in front of the other instead of having one of the side. Build a step for the one in the back. This way you would have a configuration exactly like a real theater