Hi eric0668,
Have you read the tutorial post here? It has all the basic information, steps, and guidelines you will need to make the best possible choices … and know how to eliminate the worst ones.
Outside of using the testing guidelines in the tutorial post for PPP (Posture and alignment, Pressure relief, and Personal preferences) … a mattress is only as good as its construction and the quality of the materials inside it and I would make sure you know the density of any memory foam and polyfoam in any mattress you are considering so that you can make sure it doesn’t have any obvious “weak links” and you can make meaningful comparisons to other mattresses. No matter how a mattress feels in a showroom … if it uses lower quality materials (especially in the comfort layers) there is a much higher chance that the mattress will soften and break down much too quickly and you will lose the comfort and/or support which is the reason you purchased it in the first place and need to replace it … and the loss of comfort and support isn’t covered by a warranty.
If you let me know your city or zip code I’d also be happy to let you know of any of the better options or possibilities I’m aware of in your area.
Phoenix