I looked at a four-inch memory foam/fiberfill combination topper at Costco today, almost bought it, but then didn't. I have an older mattress/box springs which definitely need help. I'm currently using an eggcrate topper, which helps, but isn't that comfortable either. My sheets fit on this combination, but with four inches of topper I'm not sure they would. Do standard deep-cut fitted bottom sheets work with these thicker toppers? Also, does anyone have experience with the Costco topper? It's 2 1/2 inches of memory foam backed with 1 1/2 inches of fiberfill so you are supposed to have a choice of a firmer or softer sleeping surface depending on which way you turn it. Another option is a new bed - I don't want to spend the money, but maybe that is the way to go long term. Thank you for any input.