From what I've read in other posts from owners of the floorstanding speakers, 7 ft might be kind of close.
Regarding distance from the wall in back of the speakers, I think you just need 6 inches or so. I have mine out from the wall about 2 feet (so that I can bring the fronts even with my TV screen) and toed in so that they form a gentle arc.
There is an article
here that I found from a Google search. Can't vouch for the validity of all of the recommendations being made, but after a quick scan of the article the spacing recommendation seems reasonable and in line with my earlier post of sitting back 1.5 times the distance between the speakers, but I think you can get away with a little less. Any more than 1.5x and you might not get a proper stereo image. Keep in mind that I didn't read the whole article so I'm not sure what else you may find in there.
I have a pair of M3ti bookshelves, which are reported to have a similar sound to the M40/M50 - they just don't go as deep. They have a more relaxed sound than the M22/60/80 speakers. As I mentioned, I have the 22's and I find the difference somewhat noticable between the two. Where the M22 (and reportedly the M60) has a very detailed sound, the M3 is somewhat softer to my ears.
If you haven't done so already, do a search on the boards and you will find a number of posts where people have described their impressions of each of the speakers you are interested in, with the possible exception of the M40's which doesn't get a lot of mention.
