I use QS4s with M40s and they sound great in a decent sized room (~400 square feet). Then again, I tend to laugh off the whole "perfect timbre matching" stuff, because most movies don't even come close to making adequate use of the surrounds anyway. Besides which, in a properly mastered 5.1 soundtrack, effects should sound differently in the surrounds because of the doppler effect.
As far as maximal dispersion, try playing with the positioning of your QS-4s. I moved mine out from the walls a bit (I use stands) and played with the angle of the nulls...a bigger difference than you might have thought.
Finally, you can always increase the output to the surrounds on your receiver. This is almost mandatory for the center channel (some soundtracks are just mixed awfully), and the average receiver will have more than enough juice with speakers as efficient as Axioms.
