Best bed for bad backs

I would like to know what you would recommend for a couple who have back issues and cant quite agree on comfort.
I like a medium bed whilst my husband likes a firmer bed. We have just brought a bed from a well known high street shop that was medium/firm with memory form top. It was bad ,after one night on it we couldn't sleep as it made us hot, and smell made us feel sick.(we did air it out)so we are trying to get our money back. My back as a lot worse when i got up.
So if and when we get our money back why should i get a bed from you.
Kind Regards
Mary