How to make my Boxspring bed more comfortable?

Hi everyone,

Apologies if this is the wrong place to ask but I was hoping someone could please give me some advice on how to make my Boxspring bed more comfortable?

My wife and I purchased it about 3 years ago and in that time we've tried various different toppers but we've both noticed that we wake up feeling stiff and not well rested; the problem is even worse for my wife who has existing problems with her hips.

Could anyone please offer any advice? I was thinking of perhaps buying a mattress (but which one?) to place on top of the bed but I wasn't sure if this would be a viable solution.

Thank you in advance to anyone who can help, I really appreciate it.