Hi Dr. Rich,
Unfortunately this is all too common. Even those who read the overviews on the site will find that they know more about mattresses than many of the salespeople who sell them (especially in the mass market outlets and chain stores) and when you start asking questions you will see eyes start to roll, evasive answers, or outright wrong or misleading information presented as fact.
This is fairly typical when you add a topper to a mattress where the foam near the top has softened or broken down. the topper will still sink into the softened foam below it (especially in the areas it has softened under the heavier areas of the body) and it puts you further away from the firmer support layers which are designed to “stop” the heavier areas of the body from sinking in too far. This is why it’s easy to fix a mattress where the upper layers are too firm (with a topper) but very difficult to fix a mattress where the top layers are too soft. Any improvement is usually minor or temporary.
There are several ways to accommodate different needs and preferences on the same mattress. You can read a bit more about them in post #2 here. A good manufacturer or retailer though will have the knowledge and experience to help with this (again so you don’t have to “be the expert” yourself) so this is just to give you the confidence of knowing that a mattress can accommodate the different needs and preferences of two very different people.
Given the retailers and manufacturers you are mentioning you have probably already seen this but just in case … the list of the better options and possibilities I know of in the greater Los Angeles area are in post #2 here.
I understand how easy it is to get overwhelmed with all the information especially on a site like this where the information base keep growing. The easiest way to bypass this is to limit the places you visit to the ones that have the knowledge and experience to give you good guidance and focus more on “finding the experts” than on becoming one or crossing the line into information overload. Too little knowledge usually leads to poor choices in terms of quality or value (especially if most of your shopping is at mass market outlets) but there is also a line where too much information can lead to information overload and paralysis by analysis.
I would also trust your body when it comes to pressure relief and alignment rather than going by “specs” about what is “right” or “wrong”. Some guidelines for testing for pressure relief are in this article and for alignment are in this article and a simpler version is in post #11 here. Keep in mind that everything boils down to the two basic functions of a mattress which is pressure relief and support/alignment and everything after that is all about preferences and making sure that the mattress you are considering uses high quality materials so the comfort and support won’t break down too quickly.
Phoenix