Hi RehabRN,
The first place I would start your mattress research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you with how to compare mattresses ad make the best possible choices … and know how and why to avoid the worst ones.
Outside of the importance of careful and objective testing using the testing guidelines in the tutorial post to assess how well a mattress matches your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) … a mattress is only as good as its construction and the quality of the materials inside it. I would never buy any mattress if you aren’t able to find out the type and quality of the materials inside it (see the guidelines here along with this article) so that you can make sure there are no weak links in the mattress and make more meaningful comparisons to other mattresses. Without this information you would be making a completely blind purchase which is very risky and is one of the most common cause of buyers remorse much too quickly after you buy a mattress.
Depending on which sites you look at … the iMattress 11 has between 3.5" to 4.5" of various layers of memory foam and polyfoam in the mattress along with an inch of latex of some type (which isn’t enough to be particularly meaningful) on top of a pocket coil. While the pocket coil would be fine because the support layers of mattress aren’t usually the weakest link in the mattress … the foam layers are easily thick enough to be a significant weak link in terms of durability if the materials are lower quality/density than the guidelines here so I would make sure you know the type and quality of every layer before you decide to buy any mattress.
If you let me know your city or zip code I’d be happy to let you know about any of the better options or possibilities I’m aware of in your area.
Phoenix