For the M50s:

16.5x27 with a fireplace to the left and a large open area behind the couch to the right. Doorways and hallways are kinda fixed so there is only one place for the 65" Mits with the speakers(unfortunately)located Inside vertical cabinets(which also contain the electronics)to either side of the TV. Even the sub has a bad spot, sitting in the corner next to the left speaker "Cabinet" firing right toward the side of the fireplace.(It's a cobbled up old 1946 theater speaker box I up-converted into a sub, has sentimental feelings, can't part with it at this moment, but due to WAF, can't move it to a spot where it can be too obvious. Not that I can find a better spot for it anyway, even playing the sub-crawl game)

For the M3s:

12.5x28, The narrower room was laid out in such a way that I could set up the system with much more latitude. We still had the vertical cabinets next to the old 31" TV, but the M3s were to the ousides of them, on stands. The sub sat in an ideal corner where even it, and the Wife, were happy!

The old house was better, but now with four Grandkids to raise, we needed more room!!
Rich.