Hi scg,
Just in case you haven’t read it yet … the first place I would start your research is the tutorial post here which has all the basic information, steps, and guidelines you will need to make the best possible choices … and know how to avoid the worst ones.
Their adjustable ultra plush that ships across the country is actually lower cost than the ultra plush sold locally and has more options available to customize it as well.
This may be well worth testing because your Englander also uses Dunlop which it seems you like.
They will tell you anything you wish to know about their latex if you talk to them but you can read some of my thoughts about Spindle and the latex they use post #6 here and post #38 here and a forum search on Spindle (you can just click this) will bring up more information and feedback about them as well. Post #6 here has more information about the different types of latex.
There is really no way to assess the quality of most of the major brand mattresses because they usually won’t tell you the quality of the materials inside it but even if they did you would find that they are not in the same quality or value range as mattresses made by many smaller manufacturers across the country that use better quality materials in the same or lower budget ranges. I would avoid major brands or any mattress where you don’t know the quality of the materials inside it.
The better options I’m aware of in the area are listed in post #3 here and this thread has some feedback that may be of some interest as well.
Phoenix