You know, I read your first post yesterday and wanted to mull it a while before responding.
I know you said that rearranging the furniture is out of the question, but I really want to talk you into it anyway.
You have a big, beautiful TV. You want to invest in really nice speakers to have a great HT experience. And you're trying to wedge the whole thing into a corner of a pretty big room.
While it is a big room, you've got a HT, a Piano, traffic patterns, a pool table and a computer. Whew! Not easy.
But honestly, if you just put the TV on the end wall and orient the speakers the long way, I think you're going to be MUCH happier whatever activity you are enjoying in that room.
If you want the M60's, get them. It is a bit harder to get them to image in a smallish space like that, but it sounds like you won't be "satisfied" unless you get them. I had them in a similar space initially, and it was wonderful. BUT I recently re-oriented everything in a different room where the seating position did not have a wall directly behind it - holy cow, what a difference!
Plus, if you put the TV and M60's on that short end wall, you'll be able to see/listen very well from the pool table area.
If you go with the TV on the end wall, I'd be surprised if you even needed the M3's that you have listed (as zone 2?). You'd certainly get much better surround from either 5.1 or 6.1 that way.
The only solution to a good HT experience in that room is to rearrange the furniture. Anything else would be too much of a compromise, IMO.
