Hi bum back,
The closest factory direct manufacturers to you are in NYC. You may already know this but you are also not in an area that has a great selection of mattress stores. Some of the better outlets that are in reasonable driving distance are in post #2 here. There are more complete descriptions of many of them in post #7 here.
Some of these are fairly far away or make some very high quality mattresses but may be in a higher budget range than you are looking for. Because you didn’t mention a budget and don’t yet know the materials you may prefer … any of the ones that attract you based on their website information and that may be close enough to justify a drive would be worth a phone call.
If NYC is a reasonable drive for you … I would tend focus on the NYC list which are likely to have better quality value choices than the options I’ve listed later in this reply
Closer to your neighborhood you would need to “interview” the local outlets to get a sense of how knowledgeable they are about the materials in their mattresses along the lines of this article.
If you are OK with doing this (and sometimes feeling like you may be pulling teeth when many of them may not know or not want to tell you the answers you need to these types of questions) … then these are the stores that may be worth some research. I’ve included some of the brands they carry that may have some better value models in their line but they would need to give you a layer description of the mattresses for you to be able to know the quality (and many outlets can’t or won’t do this). High quality materials like latex, higher density memory foam, or higher density polyfoam is important for durability with higher weights especially (as you have seen).
If nothing else these outlets would give you a good place to test various materials or types of mattresses to see which you preferred even if you don’t end up purchasing there.
http://www.onestopsleepshop.com/ Coram, NY. Eclipse, Therapedic, Eastman House, Gold Bond, Pure Touch Latex (Therapedic).
http://www.mybobs.com/naturally_bobs_latex Nesconset, NY and other locations. The only mattress I would consider here is the Naturally bob’s and I would want to know the details of the materials (the type of latex and the density of the base foam). See post #4 here before you consider these.
http://www.shirleysleepshoppe.com/ Shirley, NY. They have no listing of what they carry but their site indicates they carry Gold Bond. Some of the King Koil heavy duty mattresses also use very good quality foams. I would call them first to see what mattresses they carry before considering a visit.
Bayshore Furniture & Mattress - (NY) Bay Shore, Bohemia, NY. Therapedic, Eclipse, Eastman house, Gold Bond
Products - IKEA Hicksville, NY. The Sultan Edsele is worth considering here because is is “mostly natural” latex and while it may be quite firm … it would be a good base for a softer topper.
http://www.sleepworksny.com/ Massapequa Park, NY. Pure Latex Bliss, Ecosense, Therapedic, Natura, Gold Bond. Pure latex bliss in particular makes some very nice Talalay latex mattresses although they are often in a higher price range than most factory direct outlets.
http://www.plazafurnitureny.com/ Massapequa Park, NY. Carries Savvy Rest component latex mattresses which use high quality materials and can be customized in different ways but are also in a more premium price range than some other similar mattresses.
http://www.furnitureexprezz.com/ Ronkonkoma, NY. US Sleep, Quality foam (long island manufacturer of innerspring/poly promotional mattresses), Enso, Coaster. Talked with Jacob and he is knowledgeable and helpful. Mostly memory foam mattresses. Check foam densities carefully to make you aren’t purchasing low quality memory foam (particularly with Enso).
Bliss Sleep Center .com Domain Name Is For Sale Water Mill, NY. Carries some high quality mattresses made by Savvy Rest, White Lotus, Royal-Pedic, and Natura which are all high quality mattresses but are also in more premium price ranges so I would make some careful value comparisons here.
Hope this helps and if you have questions along the way feel free to ask 
Phoenix