Was cost an issue why you didnt' buy Qs8's for the left/right surrounds? They will really out perform a direct radiating design like the m3i's. The rear channel does not get as much information sent to it, like the left/rear channels, that is why some still stick to 5.1.
Currently I don't see a huge difference between 6.1 and 7.1 as both channels get the same information sent to them. Many people just put one Qs8 or Qs5 back there since you have the 2 tweeters firing in 2 directions. Many people also put the Qs8's on stands if they can't accomodate ceiling mounted configurations.
Axiom has great customer service, so you could always get one more Qs8 and put them as your left/right surronds, I think you would find you would get a lot more performance than a bookshelf M3i
