What's the feeling regarding M2 vs. M3?

I'll have to place the rear surrounds above two windows in the rear of the room...either wall mounted directly above each window OR ceiling mounted a bit in front. In either case the rears will be mounted significantly higher than the left and right side surrounds so I'll likely have to angle them a bit down toward the sweet spot. Do any of my rear surround choices lend themselves to this placment? Any suggestions on mounting, aiming, etc?

Thanks a ton for all the help...much appreciated!