medium/firm best mattress for us?

Hi. My hysband has a bad back and likes a very firm mattress and U have back discomfort abd like a medium leaning towards firm mattress. We have a sealy mattress at the moment (indulgence ir something like that) on a slated bed. The slats seem quite rigid and the mattress is 8 years old. I'm 10st and he is 11st. He hates memory foam and the 'sinking into bed' feeling Do you have an option for us?