The problem with getting another litter box is that there is literally nowhere else but where we moved the old boxes to. We had one box in the baby's room on the second story since we got the girls, and the other box in the alcove in the basement. Since we don't want the baby's room to smell like cat poop (and we're also going to be painting/decorating soon), we moved the box that was upstairs into the laundry room in the basement - which is RIGHT next to the alcove where the other box had been. We also moved the alcove box into the next room, right next to the other box. We showed all four cats where the boxes were.

We don't want any litter boxes on the main floor or the second floor. We want them to be in the basement - namely, the laundry room. And there's really nowhere to put a 3rd box, unless we kept the one in the alcove and two in the laundry room - which defeats the purpose of cleaning out the laundry room to move the stuff in there so it wouldn't stink up the finished part of the basement.

Sorry, I'm rambling. I just don't get why they would poop NEXT to the litter box when it was put back exactly where they wanted it!