Welcome aboard!
On to the questions:
1) The M60ti is more forward sounding, the M40ti is more laid back...a bit more mellow.
2) How far apart will the speakers be, and how far away will you be sitting from them? The M60's do enjoy some space. I'd say you want them at least 6' apart and you should be able to sit back about 10' away from them at best. Your room isn't all that big, a pair of M22ti's and a sub may be a good choice as well.
3) see last comment
4) I wouldn't lay a M40 on it's side, and it's also far too large and heavy to put on top of your tv. Not a good idea.
5) You can use your current speakers in the rear, but tonaly they may not match the Axioms. I also have to say that the QS8's are BY FAR the best surround speakers I've ever used. Use your Kef's now if you need to, but save some money up and get the QS8's eventually.
6) As far as I know nearly all recievers have a tuner. No harm in having it, even if you don't use it. You could always get separates if you want. I have the Rotel RSP-1066 processor and RMB-1075 amp and love it.
7) Yes I believe you can, but why would you want to?
Good luck! I'm sure you'll get plenty more advise.
