Hey Omni,
I have not heard the B&W CM series but I have heard their 800 'Diamond' series. I honestly believe that the Axiom LFRs or M100s are better although at this level differences are small.
Having said that, I like my movies big and loud and my music even louder, and I've sunk some money in amps so that I can enjoy both. For movies I do enjoy a wide Soundstage and have the Axiom VP180HP to help ensure the dialogue is well centered on the screen.
How much room is best for the LFRs? Probably more than I have, but the results are still quite acceptable. I probably have about 18 inches behind each of them and less on each side. There's a boundary switch on the DSP that can be used to tweak the sound but I don't remember if I tried it!
