Titan Plus (firm level 9) for average weight sleepers?

hi, my partner and I are sleeping on the oldest, wackest mattress and we’re OVER IT. I’m 140 lb and he’s about 160, so we’re not overweight, but I’m a back sleeper and he’s a stomach sleeper, so we’ve been looking toward firmer mattresses. the idea of a brand for heavier sleepers is intriguing as I suspect they’ll be less prone to sinkage, which is my fear. however, I don’t want to buy something TOO firm for our weights. I know Titan has a medium one but people have said it’s soooooft. ideas? thoughts? experiences? we want something new SOON.