Have a look into latex if you want maximum support / durability. Latex mattresses are, in general, more resistant and bouncier than memory foams. As with memory foams though there are different firmness levels available. I like medium firmness as a side sleeper. Latex also sleeps cooler than memory foam. But again there are cooling technologies available for memory foams. Concerning mattress-in-a-box brands, you may check out PlushBeds or Eco Terra (same company). They manufacture and sell them themselves with no middleman. As far as specific mattresses, the Botanical Bliss in medium works perfectly for me. It is extremely supportive and gentle on the back, shoulders and hips. I have sciatica from years of weightlifting and it has helped considerably as it doesn't make you sink. The Luxury Bliss is also pretty good. It is a hybrid organic latex. Its coil core provides very strong support / durability and is particularly suitable if you are a heavy person. All of these mattresses are organic, hypoallergenic, fiberglass-free, don't smell, sleep cool, etc.