Hi supergirl1348,
Just in case you haven’t read it yet … the first place I would start your research is the tutorial post here which has all the basic information, steps, and guidelines you will need to make the best possible choices … and know how to avoid the worst ones (which would generally include major manufacturers and chain stores like the Brick)
Outside of testing a mattress for whether it is a suitable match for you in terms of PPP … a mattress is only as good as its construction and the quality of the materials inside it regardless of the name of the manufacturer so you would need to find out the specifics of the mattress to be able to identify any potential weak links and make meaningful comparisons with other mattresses. These aren’t really meaningful specs that tell you much if anything about the quality of the mattress.
To assess a mattress what you need is a list of all the layers and components from the top down that includes the type and thickness of each layer and component (so you can make sure they add up to the thickness of the mattress), the density of any polyfoam layers, and the type and blend of any latex in the mattress so you can compare them to the guidelines in the tutorial post. Once you have this you can make sure there isn’t more than about an inch or so of lower quality/density materials in the comfort layers of the mattress which can become the weak link of the mattress. If a manufacturer or retailer either can’t or won’t provide you with this I wouldn’t consider the mattress. Sealy typically uses fairly thick layers of lower density polyfoam in the comfort layers of their mattresses which I would avoid but at the very least you would need to know the details of all the layers (which they are unlikely to provide you) or I would pass the mattress by.
Some of the better options or possibilities I’m aware of in Southwest Ontario are listed in post #8 here.
Phoenix