Hi jaypugh,
The first place I would start is the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and know how and why to avoid the worst ones.
I would be very cautious about using reviews or other people’s experiences (especially if they are not particularly knowledgeable about mattresses which is the case with almost all consumers that write reviews) as a guideline for what may work best for you (see post #13 here). What works well for someone else may be completely unsuitable for you to sleep on. I would also be very cautious about choosing a mattress which had 3" of 3 lb memory foam in the comfort layers which is a lower quality and less durable material than higher density memory foam. You can see some of the foam quality/density guidelines I would suggest in post #4 here.
If you are considering an adjustable bed with your mattress I would consider them to be two separate purchases. I would choose the mattress first because that’s the most important part of the combination and then choose an adjustable bed based on comparisons between cost vs features that are important to you. There is more about choosing an adjustable bed in post #3 here and the adjustable bed thread it links to. If it turns out that both of them are the ones that you would otherwise choose (both the mattress and the base) after you have compared each of them to the other options you have available then of course it would make sense to buy them together.
There is also more about Sleep Science in general in post #2 here and the Emma 10" mattress in particular in post #2 here. Once again I would avoid any mattress that used more than about an inch or so of 3 lb memory foam.
While it appears you are leaning towards memory foam … I’m not sure if that’s by “default” or because you believe it’s a better material than other options that are available to you or if you actually prefer it compared to other comfort materials that you have tried. If you haven’t tested other types of materials I would take some time to do some testing to confirm which type of mattresses and materials you tend to prefer. Memory foam, polyfoam, latex foam, are the most common foam materials used in comfort layers and innersprings of various types, polyfoam, and latex are the most common support components and each combination will have differences between how they feel and perform that can fit the needs and preferences of different people.
Post #4 here also has more about buying a mattress from Costco.
The better local options and possibilities I’m aware of in the Dallas/Ft Worth area are listed in post #4 here.
Phoenix