Ravi, what strikes me from the numbers you give is that possibly the distances of the M80 woofer cones from the three closest room surfaces(back wall, side wall, floor)are too nearly equal to each other and may be causing a dip in the upper bass area around 100-150Hz. The floor distance is pretty much set, but experiment with small changes in the distances to the walls. Keep in mind that the best location for the low bass is right in the corner, often the best location for a single sub, but that placement would cause frequency variations higher up for full-range speakers and isn't a good idea. This is why you hear better bass when you're in the corners, while it's weaker at your usual 10' position, which is close to the null position for both the front to back and side to side room modes. No easy solution, but experiment with both speaker position and your listening position.
