George, having owned the M60's prior to upgrading to the M80's and having similar restrictions in placement, I can tell you that I found with the 80's I needed a minimum of 8 inces from the rear wall for them to sound right, the 60's were more forgiving and could be placed several inches closer.
I orginally had my 60's about 4 inces from the rear wall and they sounded great, when I upgraded to the 80's and put them in the same footprints they sounded terrible, I then pulled them out about 4 inches and they sound fantastic. If you can leave some room the 80's are great, but the 60's are also terrific speakers, you can't go wrong with either. Hope this helps, good luck with your choices.
