I have a similarly shaped room, in that it is wider than it is deep. I have M80's a VP150 and 4 QS8's. The imaging of the center channel, I have found, is not the issue; no matter where you sit, you know that voices are coming from the center. The issue I had was the imaging of the L and R speakers. Positioned perpendicular to the back wall, gave the person on the left an earfull of left channel and not much of the right - same for the flip side. I currently have quite a bit of toe-in (L/R pointed right at center listening position) and this has helped tremendously. From the far left seat, the L speaker is 10' away, but the R speaker is 17 feet away.
For the sweet spot, the toe-in has narrowed down the sound stage a bit, which is not too apparent when watching movies, but more apparent when listening to two channel.
The QS8's are so forgiving (and so good at what they do) that I think one could mount them across the front wall and they would still do their job!
You should be very happy with your purchase. Of course, we'll require pics when you're done.
