I have the X5s and sit between 10 and 11 feet away from them. In my experiments in my room this is the ideal distance and I can sit 15 feet away as well. 8 to 10 feet was still very good but 10 feet was better.. I believe there is a misconception that the x5s need at least 15 feet to sound good and that it is advised on the internet if you can't sit close to that distance then the m series are recommended. I do believe if you can't sit at least 9 feet away you'd probably recommend the m series.
Yes, your right. Its important to realize that when I talk about room interference effects increasing with distance and that the X Series helps, that doesn't mean the speakers need to be distanced that far from you. They measure and sound integrated somewhere around 7 ft away, so no issue there.