For starters, welcome. Couple things maybe. I would start by making sure all speakers are set to small, and the xo is set in the 80-100hz range. I’m assuming in that small of a space, the couch is right up against the wall. In that case, and with the sub in a corner, I would agree that you should be getting some good slam. The problem is most definitely the room, more than the sub. Square rooms tend to be problematic for acoustics, and especially bass. Bass tends to get vacuumed out like you’re in outer space, so setup can be trickier. Hopefully someone with “square room” experience can help further. Ideally you’d have measurement equipment and graphs to evaluate, but that’s a different turn in the rabbit hole.