Hi nancymariec,
Although it would depend on the specific of the mattresses you were comparing … Lady Americana would probably be a better choice than most mainstream manufacturers. Lady Americana factories would also be more likely to provide the specifics of the materials inside their mattresses so you can make more meaningful comparisons but this always depends on which factory is producing them and sometimes on the specific mattress you are considering. I don’t know how transparent Soundsleep is with their retailers although other Lady Americana factories are very transparent.
I did do some looking in the Corvallis area and made a few calls (although I haven’t talked with each of these) and the better options or possibilities I could see and the manufacturers they carry that I would consider as a “possibillity” (subject to the guidelines here) are …
http://www.thesleepcentermattresses.com/ Corvallis, OR. Lady Americana.
http://www.blackledgefurniture.com/ Corvallis, OR. Englander
Chateau Home Furnishings · Home Page | Corvallis, Oregon | Your Willamette Valley Home Furnishings Store Featuring Sofas, Chairs, Beds, Mattresses, Dining Sets, and Fine Furniture of All Varieties Corvallis, OR. Englander, Mlily. Said he would get foam specs if asked.
http://www.inkwellhomestore.com/ Corvallis, OR. Carries FXI (Anatomic Global) memory foam mattresses. Said they would call their rep for foam densities.
http://maniadeals.com/matty/ Corvallis, Albany, Eugene, Springfield, OR. Restonic, Easyrest, Lady Americana
http://www.thefoammancorvallis.com/ Corvallis, OR. He sells 2.0 lb and 2.7 HR polyfoam layers which are both good quality materials but no memory foam and you would need to get a cover to use these in a DIY mattress.
http://athomesuperstore.com/ Albany, OR. Northwest Bedding, Englander, and Thomasville (Boyd) latex is coming.
http://furnitureandbedsoforegon.com/ Albany, OR. Carries Northwest bedding and Englander (including latex and two sided innersprings). Will call for foam densities.
http://www.parklanemattresses.com/ in Portland is one of the members of the site. They have a wide selection of different types of mattresses (innersprings, latex, memory foam etc), use good quality materials and have great value. I drove down to their Tualatin factory outlet from Seattle and was very impressed. They have stores in Beaverton, Clackamas, Gresham, Sherwood, Lake Oswego, Tualatin (factory outlet), and Salem in Oregon.
http://www.mattressworldnorthwest.com/ Salem, OR. They carry OMI (latex), Englander, Easyrest. They also said they would provide foam specs.
Hope this helps 
Phoenix