Hi Chill,
Thanks for the comments 
Do you have a link to the Elara? I didn’t see a King Koil model with this name and the only “Elara” I could find is a Simmons which you can see here. It uses lower quality foam (the base is only 3 lb memory foam and 1.65 lb polyfoam) and the upper comfort layers uses P50 foam (which is @1.5 lb). I would avoid this one completely if this is the mattress you meant.
You can see my thoughts on all the iComfort models here (in case you haven’t see it).
Wide weight differentials can be particularly tricky. Because of your weight … I would focus on higher quality materials in the comfort layers in particular. With sleeping hot added to the equation … I would also tend to avoid memory foam or at the very least use the coolest memory foams available. Several options for these types of situation would be to use a comfort layer where there are several layers instead of just one layer. This is because whatwill feel soft for someone that is heavier will often feel firm for someone who is lighter. If you were to use for example 2" of softer material and 2" of medium material on top … then the entire 4" would be your comfort layer and then firmer layers below this would act as your support layer. Because of your wife’s lighter weight the 2" of medium material may act more as a support layer (the medium would “act” soft for you but would 'act" firm for her) which may give both of you the pressure relief and support you need. The other option would be to use “split” layering where each side of a mattress was layered differently for each of you. These are not “specific” suggestions (in terms of the specific layer thickness that may work best for you) but ideas that are meant to show how a mattress can be layered that can be suitable for two people with very different needs and preferences.
Some general guidelines that may help avoid most of the “worst” choices and help focus on the better choices (in terms of quality and value) in mattress shopping are here.
The overviews in the mattresses section of the site would be well worth reading to get a general idea of the materials used in mattresses and the types of layering that may work best for different combinations of weight and sleeping positions. Pages that include some general “weight guidelines” are here and for “sleeping position” guidelines are here.
There are quite a few options in the Dallas/Ft. Worth area but you will find the ones that I believe are your better choices in post #2 here.
The “pillow thread” is here
I sleep on a 2 sided talalay latex mattress made by one of the manufacturing members of the site (see the Dallas thread I linked previously). I added a note to the comments in the Dallas thread because I don’t believe they offer talalay latex any more.
Hope this helps
Phoenix