Hi evands,
Outside of PPP (posture and alignment, Pressure relief, and your Personal preferences) … a mattress is only as good as its construction and the quality/durability of the materials inside it. Unfortunately the major brands such as Stearns & Foster tend to use lower quality and less durable materials in their mattresses than I would consider and I would avoid them completely (see the guidelines here).
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses.
I would keep in mind that price is not a good indication of the quality and durability and a higher priced mattress can often be a lower quality and worse choice than a mattress that is in a significantly lower budget range. Your maximum budget is certainly much higher than you need to be able to purchase a very high quality and durable mattress that uses premium materials.
Outside of Jonathan’s suggestions (and the Naturepedic mattresses are certainly high quality mattresses and don’t have any weak links in their designs) … some of the better options and possibilities that I’m aware of in the Atlanta area (always subject to the “value” guidelines I linked earlier) are listed in post #2 here.
Phoenix