Hi Diddlydo,
Thanks for the heads up about PM Bedroom Gallery in Minnesota no longer carrying the all latex Platinum Dreams. Their sister store (Penny Mustard) still does but the brother that runs PM decided not to carry them any longer although they still carry Platinum Dreams.
I think the first thing I would do is focus on the mattress itself which is your primary purchase without considering how it may feel on an adjustable bed in different positions (this is a sales technique that is often used to sell a mattress). Any suitable mattress (foam or an innerspring that can bend) can be used on an adjustable bed so I would only test mattresses in the flat position. Once you have decided on a mattress based on its own merits … then you can consider adding an adjustable foundation to your purchase.
A mattress is only as good as the construction and materials that are in it so I would never consider buying a mattress where I didn’t know the specific details of what was in it. “Foam” is way too generic a description and could mean almost anything from “throwaway junk” that won’t last to very high quality. You can’t feel the quality of a mattress in a showroom because low quality and high quality materials can both feel great. Low quality doesn’t stay feeling great for very long however. The best way I know to buy a mattress is to follow the steps in post #1 here. This will help connect you to better manufacturers and retailers that are more committed to helping you find a mattress that best meets your needs and preferences and has the best possible quality and value in your price range without resorting to gimmicks or sales techniques to sell a mattress.
Once you have decided on a mattress then you can consider whether or not you want to add an adjustable bed as an option.
For most people … an adjustable bed is a luxury and not a “need”. It’s used for reading, watching TV or a movie, working in bed on a laptop, a meal in bed, or for some of the other optional features such as massage. We have one and for these things it’s great and each person can decide for themselves if the cost is “worth it” based on how they feel about the options they make possible and on how much they think they would use them.
In some cases they can also be used for medical reasons which can benefit from elevated sleeping such as acid reflux or some heart or circulatory conditions etc. Some beds even have a snore position so if one half of a couple starts snoring (on their back) the other one can elevate their torso slightly which can often stop the snoring and then after a timed interval the bed goes back down but this would generally need a split adjustable and mattresses that can operate each side independently.
If you are an exclusive back sleeper and don’t sleep in any other positions (side or stomach) then there are also benefits that can come from elevating the knees similar to putting a pillow under the knees because this can rotate the pelvis and relieve some pressure and stress on the lumbar area and can help with some circulatory conditions as well. If you sleep in any other positions (side or stomach) then having the bed elevated is of course not really suitable except a small amount of elevation in the foot of the bed can still be OK for some side sleepers and can help when they are on their back.
If you are considering an adjustable bed it would be important to check with the manufacturer or retailer of the mattress to make sure that the mattress is suitable for use on an adjustable base and that using an adjustable base wouldn’t damage the mattress or void the warranty. In general terms … foam materials such as latex, memory foam, or polyfoam along with most pocket coils are “bendable” and flexible enough to use with an adjustable bed but thicker layers of firmer polyfoam or thicker mattresses may not contour as well to the different positions and in some cases the constant bending can affect the durability of the foam so I would always make sure you confirm with the manufacturer or retailer that your mattress is suitable for use with an adjustable bed.
Since most of the well known adjustable bed manufacturers are reliable … I would choose between them based on price and features comparisons that include the features and benefits that are most important to you. The adjustable bed thread here has more information that you can use to make price/features comparisons between the more popular manufacturers and also includes some links to some sources you can use for pricing reference purposes (there can be a wide range of prices for the same models from store to store).
When you are testing mattresses though … I could compare them based on their relative quality and value and on their suitability for your specific needs and preferences without regard to how they may feel on an adjustable bed because an adjustable bed and the benefits that come from them can be used under any suitable mattress (that can bend). Again though … I would consider the purchase of an adjustable bed as more of a features vs price purchase because all of them perform the same basic functions and the main differences between them are the additional features and options they have.
Phoenix
@whoever,
[quote]gravity pulls us down the longer we sleep
This guy must be an unemployed physicist. [/quote]
That must be true. If he was an unemployed gerontologist or plastic surgeon he would have said “the longer we live the more gravity pulls everything down” and been selling something else completely 
