Hi mojowomyn,
An adjustable bed can acertainly help as you know but it doesn’t limit your options too much because almost any foam mattress (memory foam, latex foam, and polyfoam) or a pocket coil will be fine on an adjustable bed. The only real limitations are an innerspring with a border wire that shouldn’t be bent.
The best place to start your research is post #1 here which has all the basic information, steps, and guidelines you will need to make the best possible choices. You will also see a recurring theme that a mattress is only as good as its construction and the quality of the materials inside it so I would never buy a mattress where you don’t know all the details and quality of every layer.
I am in the market for a Twin XL for myself, and I can spend up to $5000. (not that I want to! lol)
This is a very high budget range for a twin XL with an adjustable bed and is probably much higher than you will need even for a premium mattress. Even if I was spending $2700 or more for a twin XL (the rough cost of the Dormeo 8500) I would make sure that it was clearly superior to any other mattress I had tested in significantly lower price ranges that was available to me in terms of PPP and the quality of the materials.
Phoenix