Hi AnointedMatt,
I would be cautious with the assumption that higher density memory foam provides better pressure relief because in many cases it certainly isn’t true. Any density of memory foam can be made in softer or firmer versions depending on the chemical formulation of the foam. There is more about the different properties that can be formulated into memory foam in post #9 here and post #8 here and there is also more about the different specifications that can affect pressure relief in post #4 here. The density of memory foam (up to about 6 lbs or so) is much more closely related to the durability of memory foam than it is related to the firmness or pressure relief of memory foam and it’s very possible that you would do better with a lower density and softer memory foam topper.
The choice of material for a topper is more of a preference choice than a “better/worse” choice but the two most popular topper materials that both have great point elasticity and pressure relieving properties are memory foam and latex. There is more about the pros and cons of memory foam vs latex in post #2 here.
While they used to be more readily available … I don’t know of any legitimate source for memory foam toppers that are currently available that are more than about 6 lb density.
The first “rule” of mattress (or topper) shopping is to always remember that you are the only one that can feel what you feel on a mattress or a mattress/topper combination and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or topper or combination of materials and components would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and Personal preferences) or how a mattress or mattress/topper combination will “feel” to you based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing (using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
While it’s not possible to make specific suggestions because of all the many variables involved that are unique to each person and your own experience is the only way to know for certain whether any mattress/topper combination will be a good “match” for you in terms of PPP … there is more information about choosing a topper in post #2 here and the topper guidelines it links to that can help you use your sleeping experience along with the other information I linked as a reference point and guideline to help you choose the type, thickness, and firmness for a topper that has the least possible risk and the best chance for success. It also includes a link to a list of some of the better online sources for toppers I’m aware of as well.
Choosing a suitable topper that is a good combination for both you and the mattress you are using it on (different mattresses will affect the choice of topper that works best for a particular person) can be almost as challenging as choosing a mattress that doesn’t need a topper in the first place (especially if there are health issues or other more challenging circumstances involved that may not be completely solvable with either a mattress or a topper) so the exchange/return policy for a topper you purchase can become a more important part of the “value” of a topper purchase just in case a topper you purchase doesn’t turn out as well as you hoped for.
If you are planning to order from Foambymail (AKA FBM or Foam Factory and other names as well) then I would read this post and this post and this topic (about their polyfoam and sources) and this post (presumably from a past employee) before buying anything or considering them as a reliable supplier.
ADDED: I don’t believe the density for the FBM ebay topper that is mentioned in the reply before mine is legitimate and I would be very cautious about purchasing anything from them based on their descriptions.
Phoenix