Hi recklessnl21,
Welcome to the Mattress Forum! 
The best advice I can offer you is to “reset” how you are going about your mattress purchase process.
The first place to 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 choice … and perhaps more importantly know how and why to avoid the worst ones.
The simplest version of the tutorial:
Choosing the “best possible” mattress for any particular person really comes down to FIRST finding a few knowledgeable and transparent retailers and/or manufacturers that sell the types of mattresses (see this article) that you are most interested in (either locally or online) and that can provide you with all the information you need to know to make an informed choice and make meaningful comparisons between mattresses and then …
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Careful testing (hopefully using the testing guidelines in this tutorial) to make sure that a mattress is a good match for you in terms of “comfort”, firmness, and PPP … and/or that you are comfortable with the options you have available to return, exchange, or “fine tune” the mattress and any costs involved if you can’t test a mattress in person or aren’t confident that your mattress is a suitable choice.
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Checking to make sure that there are no lower quality materials or weak links in a mattress you are considering relative to your weight/BMI range that could compromise the durability and useful life of the mattress (see the durability guidelines here)
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Comparing your finalists for “value” based on #1 and #2 and all the other parts of your personal value equation that are most important to you.
As I think you’ve already read, the major brands such as Sealy/Stearns & Foster, Simmons, and Serta all tend to use lower quality and less durable materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely relative to the price you pay which is why I would generally suggest avoiding all of them completely (along with the major retailers that focus on them as well) regardless of how they may feel in a showroom along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it.
While I can certainly help with “how” to choose … It’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
No such lists exist, nor would it be possible to maintain, because of the ever changing landscape of tens of thousands of mattresses that are produced. In addition, no one can feel what you feel and there is no general consensus upon comfort recommendations or scales.
It is common for mattresses using lower density foams to have a comfort life only in the 3-5 year range.
The better options or possibilities I’m aware of in and around the Nashville area (subject to making sure that any mattress you are considering meets the quality/value guidelines here) are listed in post #7 here.
Phoenix