Misfit,
I am currently in the inverse situation as you are describing. I have M60's up front, VP150 for a center and a set of M22's as rears, all in a 5.1 setup. I have only had my Axioms for a bit over two weeks and they blow my previous HTIB speakers out of the water and off the planet. I live in a rent house and did not want to have to hang the QS8's on the walls and then have to fix the holes before moving out. I "plan" on (when we move into our "own" home") to replace my receiver with a 7.1 capable one and adding a set of QS8's in the locations you are describing.
Now, what I can comment on is using the M22's as surrounds. Yes, there is a bit of directionality (is that a word?) but they still throw a very large soundstage (albeit not as "immersive" as the QS8's should), toed in of course... Once I thought that some small creature was behind my chair during the "Journey through the Marshes" scene on LOTR: TT...not to mention the marsh bubbling, rustling noises, etc...
I went with the M22's to try to match the M60's timbre although I have not heard the M2's. BTW, I have the M22's on 28" stands near the rear corners of the room...not the best location but the best afforded by the room.
Just my .02,
WhatFurrer
