Hi KBPuyallup,
I’m glad you found us … and welcome to the site 
Just in case you haven’t read it yet … the first place to start your mattress research is the tutorial post here which has all the basic information, steps, and guidelines that you will need to make the best possible choices … and know how to avoid the worst ones.
The tutorial post also includes some testing guidelines you can use which for a local purchase is the best way to choose a mattress that works best for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). There are too many unknowns, variables, and personal preferences involved for anyone else to be able to tell you which mattress is best for you based on what I call on “theory at a distance” (see mattress firmness/comfort levels in post #2 here)
Other than PPP … the most important “quality” specs you need to know to make an informed choice are in this article and you can use the guidelines here to help you identify any weak links in a mattress and make more meaningful quality and value comparisons based on the parts of your personal value equation that are most important to you. Of course you’re also welcome to post the specs of any mattress on the forum and I’d be happy to make some comments about them but they would need to include all the “quality specs” I would need to make any meaningful comments about a mattress.
You would need to list the density of all the foam layers in the Lady Americana mattress you listed for me to make any meaningful comments about the quality of the materials but I do know that the foam specs in all the Rocky Mountain mattresses are good quality and all the polyfoam they use is at least 1.8 lb density and that none of their mattresses have any obvious weak links in their design or construction in terms of the quality of the materials.
If you are considering a mattress that is sold online where you can’t test the mattress ahead of time for PPP … then a more detailed conversation with a knowledgeable and experienced manufacturer or retailer who has your best interests at heart can help them to help you choose which of their mattresses is likely to be the best “match” for you based on the averages of customers that are similar to you.
The tutorial post also includes links to some of the better online retailers and manufacturers I’m aware of (which includes Rocky Mountain Mattress).
The better options and possibilities I’m aware of in the Seattle/Tacoma area are listed in post #2 here.
Phoenix