Mattresses for larger people

Hello! I am excited to find your website because it looks like a very honest and comprehensive guide to mattresses. My husband and I are in the market for a new bed and mattress, and I am after some advice on what would be best for us. We're both heavier people. I am about 17 and a half stone, and he is somewhere around 18 and a half stone. Neither of us is particularly tall.Currently we are sleeping on a king-size slatted bed with a pocket-sprung mattress. We're thinking of getting a super-king divan bed (we've had to replace so many slats and we're obviously too heavy for them) but we're stuck on what kind of mattress to get. We both sleep on our sides (myself religiously, but my husband rolls onto his back sometimes). I swap from side to side, but I am now finding that my hips are aching a lot even though I try to stay well aligned and use an orthopaedic pillow. Basically, it feels like our mattress is too hard for me, but I don't know how to go about finding something that feels softer but that still has enough support for our body weights.We appreciate that meeting our needs might well come at a cost. We're at a point where we are happy to invest in a decent, well-built set up, but I'm worried about making a bad decision. Please could you give me some advice on the best product for us: something that will support heavy people, while feeling soft enough for a sensitive side-sleeper. I really look forward to your reply!