Hi missy,
The most effective way to buy a mattress is to learn just enough that you can ask better questions (just scanning the overviews in the mattress section is usually easily enough) and then to find the 'experts" in your area that can help you make better choices. There are a large number of better sleep shops and/or local factory direct manufacturers that are very knowledgeable and carry higher quality and value mattresses than the typical mainstream outlets or major brands. They have the knowledge, skill, and experience to help you make much better choices than trying to learn everything yourself. What they already know you don’t have to learn and then instead of going by theory … you can actually lie on mattresses that use the materials you are interested in and listen to what your body tells you.
If you let me know the city or zip where you like I’d be happy to let you know of any better outlets or factory direct manufacturers I’m aware of in your area.
I also think Post #2 here may be very helpful.
Once you’ve found the best places … then you can focus on finding the best mattress or layering using someone else’s knowledge, willingness and ability to help you in real time and in person. It’s much less confusing and frustrating than the other way around.
Phoenix