Hi travandsteph,
Just in case you haven’t read it yet … the first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines you will need to make the best possible choice no matter what your budget range or the types of mattresses you may tend to prefer. It will also help you to know how and why to avoid the worst choices.
There isn’t a member of the site in the Seattle area that sells memory foam mattresses but if you are at step 3 in the tutorial post and are ready to start testing mattresses then the better options and possibilities I’m aware of in the Seattle area are listed in post #2 here.
Nobody else can feel what you feel on a mattress and this link in the tutorial post talks about how there are too many unknowns, variables, and personal preferences involved for someone to know which mattress may be the best match for someone else based on specs (either yours or a mattress) or “theory at a distance”. The only effective way to choose a mattress that is likely to be a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) is either with careful testing using the testing guidelines or when you can’t test a mattress in person then with a more detailed conversation with a knowledgeable and experienced online retailer or manufacturer who can help “talk you through” the options that they have available and who will know more about “matching” their mattresses to different body types and sleeping styles based on “averages” than anyone else.
If you follow all the steps in the tutorial one at a time you will have the best possible chance of making a great choice. I’m looking forward to finding out what you end up deciding … and of course any comments or questions you may have along the way. 
Phoenix