Seems like getting a second sub is the way to go to fix this. Still works out cheaper than buying decent 3 way monitors, I guess. Can MA1 configure/manage multiple subs? Sorry I haven't updated the app in a while.I had the same issue when I used only one KH750. It was on the left-hand side of my desk, 1/4 the width of the room, I was able to locate the bass. Then I have bought an additional KH750, put it on the right side of my desk at 1/4 room width and now it's perfect.
But if you have the space to place a big monitor, it might be the better solution.