If they are as crowded as it sounds I would give them another box with drawn comb or foundation. They need the space and this should give you some time to get your ducks in a row for you split, or splits if that great queen starts to lay in the new box. Even if she does not it gives them room to start storing the nectar coming in they will be competing with her for empty cells in a packed brood chamber with nowhere else to put the sweet stuff.