Back issues here too.
It was hard for me to choose between Sleep Number and Temperpedic. I ended up listening to the advice of my very good massage therapist. She told me that her clients preferred Sleep Number over Temperpedic by a wide margin.
I chose a Sleep Number model that had that a big layer of that gel foam stuff on top. Kind of like the best of both worlds. It was big time comfortable. BUT...I got real hot laying on it. I'd wake up and night burning up. That gel foam stuff doesn't breathe. Sleep Number swapped me out for a different model with a more traditional top, free of charge and free delivery no questions asked.
I'm really glad I didn't go with the company that only makes gel mattresses.
I'm really happy with the mattress I ended up with and I am glad I didn't pick a company that only makes gel foam mattresses. I might have been happy with Temperpedic, but if I wasn't they wouldn't have had an alternative.
I also favor the adjustibility of Sleep Number. With everybody else's mattress, you get what you get and that's it. Other mattresses will also wear over time. The core of a Sleep Number mattress is never going to wear. You might replace the top pad over time (but I doubt it). I think this is the last mattress I'll buy.
Pro Tip: the "platform" that Sleep Number has, which they sell in place of box springs which aren't needed anymore...is just an expensive plastic box. You could save a lot of money by not buying their platform and just build something from lumber. But if you did I think they wouldn't honor any warranty.