Hi suzan,
While US Mattress themselves may be reputable … they can only provide you with the information that they are able to find out from the manufacturers that they carry.
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 but outside of PPP (Posture and alignment, Pressure relief, and Personal preferences), a mattress is only as good as its construction and the quality and durability of the materials inside it regardless of the name of the manufacturer on the label and I would avoid all the major brands and any mattress where you aren’t able to find out the specifics of the materials inside the mattress so you can identify any lower quality materials or “weak links” in the mattress (see this article for the information you would need) and make more meaningful comparisons with other mattresses you are considering.
The first place I would start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that you will need to make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Phoenix