Since the M80's woofers are facing the opposite wall (another long wall), I’ll bet the low frequencies are bouncing. At this point I'm 100% sure that your problems are acoustic related.
Can you try moving the M80's to the short wall and have it firing toward the long part of your room? This way you will know that the M80's are not the problem. Keep in mind that this is just an experiment. I’m not trying to tell you that you have to upset the misses by rearranging the room.
Let us know if you do the experiment and what the results are.
Good luck!
Tom
P.S. Don’t worry too much about the spelling. We all make mistakes.
