The list you have at the end of your post will help. Anything you can do to soften hard surfces will improve the acoustical properties of the structure.
Don't give up on the cellulose insulation. A simple cellulose installation will result in the cells settling. You need to have the cells "dense packed". By installing the cells at a certain density (pounds per cubic foot) they will not settle.
Not all cells installers have blowers capable of dense packing, so ask around.