Sorry for the delay in replying. Yes, the 6th speaker would be in a corner directly across to the TV corner. I have heard opinions saying if you already have QS8s, it would help to get a speaker which would not be so diffuse in reproduction, like M2. Is that true?

My gear:

HK 525 receiver
Panasonic CP-75 DVD player
M22s, VP150, QS8s, Hsu VTF-2
Samsung HLN617W DLP TV