Hello Armand,
In rooms the size of yours, the sense of envelopment produced by the QS4 quadpolar dispersion is, I believe, superior to that of a direct radiator used as a surround channel speaker. QS-4s are also very accommodating in terms of positioning in a room. They can be at different heights and still deliver a finse sense of immersion in the surround field without losing rear-channel direction cues with Dolby Digital 5.1.
If you can position the M3Ti's in an ideal position (on the side walls) in a larger, more reverberant room, the differences between monopolar speakers like the M3ti and the multipolar QS-4 aren't as noticeable.
I'd opt for the QS-4s, but it really depends more on the particulars of your installation.
Regards,
