Hi 5tevie,
The first place I would start your research is the mattress shopping tutorial here which has all the most important information, steps, and guidelines you will need to make the best possible choice in any budget range … and perhaps more importantly learn how and why to avoid the worst ones (including most of the mattresses you mentioned) … all in one place.
It should also help you “dump” much of the marketing information you have probably been exposed to in the types of stores that would typically be carrying the mattresses you mentioned and focus on the more “educational” information that is much more important and relevant to making an informed purchase and making meaningful comparisons between mattresses.
Once you are at step 3 in the tutorial and are ready to start testing mattresses … the better options or possibilities I’m aware of in the Birmingham area are listed in post #57 here. The tutorial post also includes links to some of the better online manufacturers or resellers I’m aware of if you are comfortable with an online purchase.
If you get “stuck” along the way or don’t know if any information you are being given is accurate, relevant, or even important, then of course any questions you have along the way are always welcome 
Phoenix