I agree with Randy. The dialog will come mostly from the center speaker so that wouldn't change. You can always use the night mode in your receiver to get clearer dialog in lower volume. As for music, the M60s are simply amazing, even at lower volume. For movies, they are awesome as well. Before getting the M60s, I used my system almost entirely for movies. Now that I got M60s, I find myself actually listening to CDs 30% of the time. My room size is 16'x13', almost the same as yours.
Personally, I think these speakers are as good if not better than Martin Logan Mosaic (US$2000 MSRP).
