Hi Noblerise,
It's nice to see someone who has done their "due diligence". While as you know sometimes everything can seem very complicated at first ... once the basic patterns of "how to look" and "what to look for" fall into place ... things get much simpler

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Some independent factory direct manufacturers in and reasonably near Boston include ...
www.worleybeds.com/ New bedford. They make a range of mattresses of all types including 2 sided all latex. Good quality and value and they have been making mattresses for over 50 years. Good people.
www.themattressmaker.com/ Brockton. Makes a range of standard mattresses as well as memory foam, latex, gel foam and anything else. Uses high quality materials and has very good value. Focuses on educating customers about what makes a good mattress and is very knowledgeable and helpful. Will also custom build.
www.gardnermattress.com/products.asp (as you mentioned). Salem, Newton, Woburn. They make high quality mattresses including part and all latex. While they may not be the lowest cost ... I consider them to be good value and high quality mattresses built by knowledgeable people. Well worth a visit.
www.jordans.com/About%20Us/Store%20Locations.aspx?source=topNav Reading, Natick, Avon, MA; Nashua, NH; Warwick, RI. Regional manufacturer which has their own house brand which includes some "partly latex" models. Better than mass market outlets but not in the same range as some of the better local manufacturers.
www.bostonbed.com/ Boston, Cambridge, Framingham, Burlington, Stoughton, Lynn. Company owned Factory direct outlets for Therapedic. Gel memory foam, latex, and traditional innersprings that use good quality materials and have good value.
www.factorydirectma.com/about.html Dracut. Factory direct outlet (not company owned) for Therapedic mattresses. Has their Gel foam line on the floor and will soon have their newer latex models as well but currently has the older latex mattresses (as of August 19, 2012).
www.mysticbedding.com/index.htm Medford. Makes mainly innerspring/polyfoam mattresses. They would be worth a visit for those who are in the market for the specific types or budget range of the mattresses they manufacture but they don't carry latex.
ecinindustries.com/index.htm Fall River. Makes a range of mattresses including latex, memory foam, traditional innersprings, and a gel memory foam line on the way. They will provide foam density specs if asked but not as a "normal" practice. They are mostly wholesale manufacturers but they do have a factory direct outlet attached to the factory.
bedworks.net/index.php Cambridge. Makes a range of futon mattresses but also manufactures a line of memory foam and polyfoam mattresses (all foam) using high quality materials in both the comfort and support layers (5 lb memory foam and 2.6 lb HR polyfoam). Also makes a line of platform beds.
At
My Green Mattress, the evergreen uses 1" of HD polyfoam in the quilting while the natural escape uses wool in the quilting (instead of the foam). The "see inside" link for the natural escape has an incorrect description that makes them look identical. Other than that they are the same. The organic dreams uses all natural talalay for the core (middle) layer rather than blended talalay which is a more expensive and slightly more "elastic" material than the blend used in the other two. Because of the thicker comfort layer ... this one would be well suited to most side sleepers.
You and your wife may do well with a similar construction as it happens. A back sleeper would normally start testing with about a 2" comfort layer while a side sleeper would normally start testing with a 3" comfort layer but your wife is much lighter which means that 2" may be all she needs for good pressure relief (depending on how "curvy" her profile is). If this is the case ... then either the evergreen or the natural escape may be very suitable. The evergreen would have an "effective" comfort layer slightly thicker than the natural escape because of the foam in the quilting. I particularly like that they are all 2 sided which will increase the life of even long lasting materials like latex. Tim the owner here is very knowledgeable and helpful and his advice will also help you.
I realize that
Custom Sleep Design is quite far away however they have a unique method of customizing their latex mattresses (using a very effective form of zoning) which would make them very suitable for anyone who had difficulty with customizing a mattress that allowed the shoulders to sink in far enough while still making sure that the hips didn't sink in too far. They can also be made with separate firmness levels on each side of the mattress for couples who have different needs that are difficult to accommodate otherwise. Bob is the owner here and he too is very knowledgeable and helpful. While they are not a low cost option ... their unique construction and design makes them a good value in a premium mattress.
Between the choices you have (primarily Gardner, Worley, Mattressmakers, My Green Mattress, and Custom Sleep)... there is no doubt in my mind that you will be able to find a high quality and value mattress that works well for both of you.
If you have any other questions ... feel free to post
Phoenix
PS: If you end up purchasing from one of the manufacturing members here ... don't forget to let them know you are a member here so you can receive your 5% discount