Hi RemiRoo,
My first choice would be to buy a mattress where you didn’t have to add anything at all and where the quality of the upper layers of the mattress were known and you could verify they were good quality. Unfortunately this is much more difficult when you are shopping for major brands or at a chain store where the quality of the materials aren’t usually disclosed … although some information is known and available for some of them (such as the iComforts). If you did choose to go in the direction of a mattress/topper combination … then the quality/durability of the topper would become the most important issue. There would be little difference in buying a mattress with thicker layers of low quality materials inside the cover in the upper layers of a mattress (which are the weak link of most mattresses) or buying a mattress with less “questionable” or low quality materials or that used higher quality materials in the upper layers only to add a low quality topper to it outside the cover that will also soften and break down too quickly (except of course a separate topper can be replaced much more easily than a complete mattress).
If there are no high quality toppers available that you can specifically test with a mattress then it’s usually better to make the best possible exchange and spend the extra money and buy a topper separately from a different source. Of course this also carries some extra risk in terms of making a suitable choice because each different, type, thickness, and firmness level of topper can feel and perform differently on the same mattress. Some careful testing on mattresses that have similar materials in their upper layers as the topper you are considering and the topper guidelines in post #2 here and the posts it links to can help you make a topper choice that has better odds of success.
In terms of “value” you are locked in to lower value because or the limitations of an exchange so quality and durability would be my primary consideration.
In most cases this type of information isn’t available with the mattresses you have available because the larger manufacturers don’t like to or in many cases completely refuse to disclose it. In some cases on a mattress by mattress basis this may be available or at least partly available for specific mattresses with more detailed research on the internet (or with a forum search here). It’s more common to be able to find out the density/quality of memory foam in a mattress than it is to find out the density/quality of polyfoam in a mattress. If you can’t find out the specifics from the manufacturer themselves then the information you find out from other sources may or may not be accurate (depending on where the information came from) and most of the research you do trying to find out the quality/density of materials will lead to frustration and dead ends. This is one of the reasons why I suggest avoiding major brands completely although in your case this may not be possible or practical.
If you look at the description of the Santa Ana Plush here … you will see that they don’t disclose the quality/density of any of the materials in the upper layers and that they are all polyfoam of questionable quality/density. This is exactly the type of mattress that I would completely avoid where there are thick layers of lower quality materials in the upper layers of the mattress.
The Port Cartier is basically the same and has 5.5" of lower quality or questionable materials in the comfort layers and I would completely avoid this one as well. Any difference between the coils is not really relevant in terms of quality because the coils (or any support system) is not normally the weak link of a mattress. Of course different coils in combination with different layers on top of them can feel and perform differently in terms of PPP but the “tech speak” about different coil systems and coil counting is really only relevant to the degree that you can actually feel the benefit of the specific coils in your testing in the mattress as a whole. You can read more about innersprings here and in post #10 here.
I would take these type of questionable claims with a huge grain of salt unless they can provide specific proof that validates them. In most cases these marketing claims are just inherent to the fabrics used in the mattress and you will often see this claim with bamboo fabrics. It’s questionable whether any of the inherent properties of the bamboo plant itself are even left by the time it’s chemically processed into a fiber that is used in fabrics. In other cases the mattress fabric can have chemicals added to it that provides these benefits but the nature of the chemicals aren’t disclosed. The main cause of allergies in a mattress (and other household items) is the waste materials from dust mites and you would be better off dealing with these using a mattress protector and pillow protector or a mattress and pillow encasement or materials that have more ventilation and humidity and temperature control that can reduce the dust mite population in your mattress and your exposure to their byproducts than worrying about the claims of “so called” anti fungal or anti bacterial materials in a mattress that are common to the materials themselves and that are used in many other mattresses.
You can see the layers of the CMG Radiant Plush here and once again you will see that there are 5" of questionable polyfoam in the upper layers of this mattress where the density isn’t known. the wool and silk fibers are good quality natural fibers that can do a great job at helping control moisture and temperature but it doesn’t say what percentage of wool and silk is mixed into other synthetic fibers and it could be a very low percentage that is used more for “label copy”. Because CMG is a smaller independent manufacturer you may be able to find out the foam densities in the mattress if you (or Sleepy’s) calls the factory so you can verify that they are at least 1.8 lb density (the lower end of higher quality more durable polyfoam) but they may also not disclose it for these mattresses and if they don’t I would avoid these as well.
If a mattress has more than an inch or so of lower quality materials then the risk of early softening and impressions is increased. Since this is unlikely I would look for mattresses that either have higher quality materials where the density is known or a maximum of 2" of questionable materials in the upper layers (which will generally mean a firmer mattress) and then add a topper to this.
Some of the mattresses they carry where the quality of the materials in the mattress may be more available from “outside sources” at least to some degree are the iComfort or iSeries lineup (see post #11 here for some examples) or the Sealy Optimum lineup (see post #48 here).
It will take some time, effort, care, and research along with careful and objective testing for PPP to make your best possible choice when you are trapped in between a rock and a hard place and forced to deal with a chain store or choose between major brands or other brands where the information you need to make an informed choice is difficult and sometimes impossible to come by.
Phoenix