Hi Harper,
Just in case you haven’t read it yet … the first place to start is the tutorial post here which has all the basic information, steps, and guidelines you will need to make the best possible choice.
The tutorial post also includes a link to some of the better online memory foam manufacturers and retailers that I’m aware of and Dreamfoam is one of these and a member of this site which means I believe they compete well with the best in the industry.
The Healthy Foundations 10" memory foam mattress uses good quality materials but they only have one option so they are really an all or nothing choice because there are no mattresses which are a good match for a majority of people in terms of PPP. There is more about them in post #486 here.
Some of the better options or possibilities I’m aware of in the Bristol, Kingsport, Johnson City area are listed in post #2 here.
Phoenix