I have had occasions on some material that I have actually unplugged and removed my center channel to ensure it wasn't on. Imaging on the M80's is that good. I have also unplugged my sub for the same reason on occasion.
Zimm, PSB is a good Canadian speaker company. There stuff is pretty good, at least from what I have read and heard in stores. I am supprised they are letting you down like this. Have you tried moving them around a bit, or moving your listening position to find a better sweet spot?
paul