I take it you are putting the M100s along the long wall?
That's how I have my M5s set up in the living room. They're 10 feet apart and I am 10 feet away. They have 5 feet of breathing room on either side. They have about 2 feet from the front wall (to the back of the speaker). The sphincter holes (you'll see what I mean when you get yours) are wide open and no sub. Even with only 2 feet to the back wall, I get nice depth. Some songs have instruments and voices right out my front window (which is situated between the two speakers). Clarity, bass...everything actually...is top notch. I could easily melt my brain with an ADA-1000 if I wanted to and I'd die in bliss...LOL!
My furniture was getting in the way so I pitched it out my front door and over my fence into my neighbor's yard. His mice now have nice homes. Try it. It's very liberating!
