Mark
I am currently using m3's in a similar situation. It looks like mine are a little bit further away from me than your set up. They are 54 inches
Two things I think you should consider is the distance off the wall because of the rear port. You need a minimum of 3 inches although I would recommend 5 for best results. The other thing I found is:
the shelf I needed to use was just a little bit too high so if I stood them up normally the tweets were too high. Instead of turing them up side down I have them on their sides with the tweets more in line with seating position. They are still slightly high but I have them toed down slightly. This has worked very nicely for me. The m3's are very nice for near field listening.
