Hi nina81,
Just in case you haven’t read it yet … the first place I would start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choices … and perhaps more importantly know how and why to avoid the worst ones.
The better options or possibilities I’m aware of in and around the Little Rock area (subject to the quality/value guidelines here) are listed in post #2 here.
Two twin XL mattresses can certainly be a good strategy for couples that have a very wide weight differential or have very different needs and preferences (see the first part of post #2 here). There are also some comments about the pros and cons of a split king mattresses (two twin XL mattresses placed side by side) vs a single king size mattress in post #8 here and in this topic.
Your budget is easily enough to be able to purchase a very high quality mattress (or split twin XL mattresses) that would meet all your criteria.
A latex/pocket coil hybrid can certainly make a great choice (see post #13 here) and they are both more resilient materials which can make a good choice for the other activities that happen on a mattress as well (see post #2 here) but of course this is also a matter of preference.
Unless you have a great deal of knowledge and experience with different types of mattress materials and components and their specs and different layering combinations and how they combine together and can translate them into your own “real life” experience that can be unique to you … I would tend to avoid using complex specs to try and predict how a mattress will feel or perform for you and focus more on your own actual testing (hopefully using the testing guidelines in the tutorial) and/or personal experience. When you try and choose a mattress based on complex combinations of specs that you may not fully understand then the most common outcome is “information overload” and “paralysis by analysis”. There are many different types of innersprings or pocket coils and there are also many different types of latex with different firmness levels so as an example one mattress that meets your general criteria may be a good “match” for you while another one that has the same general specs may be completely unsuitable for you to sleep on.
There is more information in post #2 here about the different ways to choose a mattress (either locally or online) that is the best “match” for you in terms of PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for that are involved in each of them.
When you can’t test a mattress in person though then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else without you needing to first go through the learning curve about mattress theory and design and the many complex specs that may be involved.
Phoenix