I pulled the speakers out about 6 inches (15 cm) further into the room (same orientation). I live alone, so I can do these things. In 2.0 mode, the bass sweep now sounds more balanced, though I lose bass reinforcement and can barely hear 40 Hz. In 2.1 mode, the low bass is still follows to the sub. I moved the sub to the center along the wall so at least it is centered. So I'm feeling a bit less hapless about the whole thing for now.