My particular problem is that the downfiring driver will basically be shooting into la-la land on both the right and rear. :-) The rear will be over an entrance to the back hall, the right one over a large opening to the kitchen (maybe 7 or 8 feet). Both the left and right top drivers have a good distance too before there's a ceiling reflection, and the first on-axis reflection will basically wind up at the TV and not at the listener. :-) The rear one has a similar reflection direction issue but is closer to the start of the sloped ceiling. Don't get me wrong, the Polks aren't ideally placed either, the openings forced me to put them about 4 feet behind the listener. But I'm currently running 5.1 and when the new receiver arrives it'll be 6.1, so I want a rear center speaker and the QS8's forward of where the Polks are now. Fortunately the back of the room is pretty live (all hard surfaces), it's just shaped oddly. Right now there's an audible gap that needs filling left to right in the rear, which is why I'm replacing the direct-firing Polks with the QS8's. I think you're right, but it'll be a lot different than the Polks which means I'm going to be tweaking quite a bit and that's not trivial with a wall-mounted speaker that weighs 11 lbs and will be 7+ feet off the floor. :-) I won't have the luxury of moving them every few days so there's the fear of getting it wrong after I've already drilled holes in the wall. I'm not sure how long my wife can live with exposed wiring, but I suspect I won't have long before I need to finalize (and run the wire through the wall and new trim). I definitely don't want to do permanent wiring more than once. :-)
I'll probably tackle some of it this weekend, but I still haven't made up my mind on the new receiver so it'll be a bit before the rear center speaker has signal. I'm still waiting on my own Sunfire Signature subwoofer too, it should be here Monday (the one I was using was a loaner from a friend, and it went back to him last week).
