For that kind of layout, with a good distance between rear surrounds and listening position, I think the M22s would be ideal.

I would take M22s over QS8s for rear surrounds in that room; however if the room were "shorter" ie the rear surrounds were going to be closer to you I would go with QS8s.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8