Hi jcl007,
The best place to start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choice in any budget range … and more importantly know how and why to avoid the worst ones (including mattress firm or any of the major brands).
Two of the more important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to buy a suitable mattress that is the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) 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 and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful comparisons between mattresses in terms of suitability, durability, and value.
If you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of that are close to you.
The tutorial also includes two links to lists of the better online choices I’m aware of and post #4 here will also be helpful for those that are in lower budget ranges.
Phoenix