Hi jianni54,
In case you haven’t read it yet … the first place to start your research is the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best choices … and avoid the worst ones.
There are too many unknowns, variables, and personal preferences for anyone to recommend a specific mattress for someone else based on “theory at a distance” (see mattress firmness/comfort levels in post #2 here) and your own personal testing for PPP is the best way to choose a mattress that is the best match for your needs and preferences. Other than this … knowing the specifics of what is in the mattress is the best way to make sure that the mattress uses durable materials and has no obvious weak links. I don’t recommend Tempurpedic at all.
There is a link to a list of some of the better online memory foam retailers and manufacturers in the tutorial post and if you let me know your city or zip code I’d be happy to let you know or any of the better local options or possibilities I’m aware of. Many of the online retailers or manufacturers sell memory foam mattresses that approximate the Tempurpedic mattresses (you can see more in post #9 here about the different ways that one mattress can “match” another) but I would tend to minimize the use of 4 lb memory foam given your experiences and weight.
Phoenix