I too suffer from a bad back and for years lay on a hard bed - orthopaedic - far too hard. I find all new beds hard - just like the suites - and I now would go for the softest bed in the shop which is "hard" enough. Good luck because buying a bed is a nightmare with a bad back.
I`ve had back & joint problems for years. No matter what type of matress I used it made no difference. I bought a memoryfoam topper & started using it on Wednesday when it arrived. I`ve had wonderful painfree nights since. I wish I`d bougt one years ago.
I have a very bad back and find that a soft but supportive bed is best. It mustn't fold in the middle when you sit on it (!) but it must mould to you. hard beds are SO painful.
I bought a Tempur mattress which moulds to your body shape and gives support wherever it is needed and am well pleased with it.
They are expensive but at least you can get a 60 day free trial which gives you the chance to try it out over a reasonable period. If it works for you and relieves the pain it will be well worth it.
A lot of bad backs are caused by the sleeping position, I know its hard for a woman, but the best position is on your back, because of the way the spine curves, if you sleep on your front, when the mattress dips, you back is bending the wrong way.
I used to have a lot of problems, but was told this by a Physio, and its helped enormously.