Which of your range to choose

Hi, we are looking to buy a new bed.
Firstly do we need to replace the base - it is a drawer base ( not sprung edge). There is nothing wrong with it and it is 6 years old?
We do have to replace the mattress - we stupidly bought a pillow top mattress because it felt so comfortable - and is to an extent, but as you can guess, we now have a pretty large lump in the middle. We have looked at your ranges, but don't really know where to go from here.
My husband is 5'9" and weights 11 stone 8 pounds. I am 5'4" and weigh 9 stone 5 pounds. We definately don't like firm mattresses and tend to veer towards softer mattresses , although husband does seem to prefer slightly firmer ones than me, although not significantly. Could you offer some advice please on the base, and which of your ranges might suit us best. Thank you.