I think QS8s for the left and right surrounds, and M2s for the surround backs.

Even if it weren't for the missing chunk of room in the bottom left, monopole backs would probably be better in this room just because of the distance.

But for the side surrounds, the QSes still would be ideal.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs