From my perspective, if you need a somewhat firm mattress, and especially if you have neck or lower back issues, I would not get a foam mattress. I have no specific recommendations, but I might try a Sleep Number or similar mattress that allows you to dial in your firmness. Good Luck!
Did the same... even upgraded the foam/temperpedic. I’m not sure if its the bed frame or mattress? Anyone looking for a new mattress, should invest in bed boards until you’ve found one you like, single size is $30 on amazon. While visiting my daughter, I slept on a very lovely medium firm innerspring mattress with a very deep pillow top. This was exactly what my back ordered. She lives in Switzerland, so the brand isn’t important... but it made me miss my old perfect sleeper!