I updated the list for the Boston region and also did some research (and made a few calls) in the Merrimack area for outlets that may have some better “local” value. These will need some further research into the knowledge levels at each outlet and to find out their ability and willingness to tell you the layers in their mattresses but I’ve listed the brands they carry that may be worth including in your research. Some of these will have latex and also memory foam, and gel foam mattresses that you can test but I would call first so you don’t visit any of them without first having a sense of their overall knowledge and service and what they carry on their floor.
http://www.mymattressmakeover.com/ Merrimack, NH. Park Place, Innomax, Comfort Bedding.
http://www.mybobs.com/ Merrimack, NH. Memory foam and latex hybrid house brand (finding out the specs would be very important here and make sure you see post #4 here before you consider these)
http://www.tuckedinorganics.com/ Amherst, NH. Carries Savvy Rest, Organicpedic and Green Sleep mattresses which all use high quality materials (latex, innersprings, and natural fibers) but are also in more premium price ranges.
http://www.jordans.com/About%20Us/Store%20Locations.aspx?source=topNav Nashua, NH and various MA outlets. Retail direct outlet for Jordans Mattress Factory which has their own house brand (I would ignore the major brands they carry). Their memory foam mattress descriptions don’t say the type of memory foam or density but the polyfoam used in the support core is a lower density/quality (1.6 lbs) than is usually used. Their latex over polyfoam mattress uses better quality poly under the latex but doesn’t give the type or layer thickness of the latex which would be important to know (so you know that it’s not just a meaningless layer hidden between other layers of cheaper foam).
http://www.richardsfurniture.com/ Nashua, NH. Goldbond
http://milliondollarmattress.com/contact.html Milford. Retail direct outlet. Carries several memory foam and latex options from Therapedic which may have better than average quality and value.
http://www.endicottfurniture.com/bedroom.html Concord, NH. Englander
http://www.yourhomeyourworld.com/index.html Concord, NH. Carries 2 natural Dunlop Latex mattresses
http://www.siestasleepworks.com/mattresses.html Acton, MA. Pure Latex Bliss (talalay latex), Spring Air. Good people and open about their materials. PLB is a high quality talalay latex line of mattresses.
http://www.butler-furniture.com/brands/ Fitchburg, MA. GoldBond (gel and visco and 2 sided but no latex on floor).
http://www.sunsetmattressfactory.com/index.htm Ossipee, NH. Independent factory direct manufacturer that makes some “old style” and good quality innerspring/cotton mattresses with working box springs that are good value.
http://lovesbeddingandfurniture.com/contact.php Claremont, NH. Carries OMI, Pure Latex Bliss, GoldBond, King Koil XL, Symbol. They understand the importance of knowing the materials in your mattress and Bobby is the “expert” here.
Hope this helps and will give you some closer local sources to test various different types of mattresses.