I need a new mattress and I'm thinking about going for one of the online brands: Leesa, Brooklyn Bedding, Casper, Helix, etc. I currently have a 12 year-old latex mattress that is sagging badly. I like the feel of latex and I really dislike the slow-response memory foam mattresses. I want a medium to medium-firm mattress that is cool and supportive without it trapping me in quicksand. Anyone have a Leesa or one of the similar mattresses?