Welcome Julien. You will absolutely enjoy your Axiom experience.
You have thrown quite a few variables into the mix here. Let me see if I can add some critical mass for you.
1) With an alternative room for using the M2s, they make sense.
2) Since you have some breating room behind the sofa, the m2s could work. Not sure about upward firing. If you are going to take that approach, it aooears that you are attempting to have the M2s be less directional/more QS8 like. Here The QS8s make much more sense since they have 2x the drivers of the M2s and already disperse sound better.
3) The QS8s will absolutely envelope you in sound. I love these things.
I have a 7 channel receiver (Denon 3803), but haven't made the trip to adding speakers for channels 6 & 7, so take that into account as you read my input. Before I take that additional step, I will try and audition 6 and 7 channel setups. Not sure that the current offerings that make use of the channels justify the extra speakers yet.
