I cant recall my dimensions but I have a large living room thats open up through the second floor, so over 20'. There is stairs and an overhead catwalk in the rear so that also probably helps reflections. There are some fake beams up on the ceiling there that may be helping things a little too, dunno. I'm also open into the kitchen area on one side. Not sure about your detail but we have the same basic shape.
I do not find the M60s bright in this area and am constantly impressed to death when I put on a CD that is actually well engineered.
For stereo only, I'm thinking they sound better than the M60s in my 5.1 HT room in the basement which is the square room from acoustics Hell. Mind you, they still impress everyone who listens down there but if I try to do a comparison, I seem to like stereo better up in the bigger room. At least what I can hear over my panting from running up and down the stairs over and over.
