Hi tbmh,
I would keep in mind that the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial)or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
There are also no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness as well and some people may rate one mattress as being firmer than another and someone else may rate them the other way around. This is all relative and very subjective and is as much an art as a science.
If the only change you want to make to your current mattress is to make it a little bit softer then it would make sense to choose the same layers and components as you currently have except to choose a top layer that is a little bit softer (perhaps 28 - 32 ILD) but once you have two designs that have more than a single relatively small difference between them then how the two mattresses compare for different people can be much more unpredictable and uncertain and the only way to really know how they compare for you (regardless of how they would compare for others that may have very different experiences or opinions than you) will be based on your own careful testing or personal sleeping experience.
There is more about the pros and cons of split layering in post #2 here.
This mattress has a completely different design and uses different types of materials, different types of latex, and different layer thicknesses than the mattress you currently own so there are too many differences to really know how it will compare to your current mattress outside of your actual experience. There is more about the pros and cons of a latex/polyfoam hybrid vs an all latex mattress in post #2 here but even if you did know the ILD of each layer it wouldn’t help you to predict how the mattress will compare to your current mattress or how it will feel “as a whole” partly because there are many other factors that can affect how firm or soft a mattress feels besides just ILD alone (see post #4 here) and partly because the ILD ratings of different types and blends of latex aren’t directly comparable anyway (see post #6 here).
Again these are both very different mattresses from the mattress you own and in the case of the Alexander it also includes memory foam which puts it in a different category again from a latex/polyfoam hybrid. There are some comments about the Alexander in post #2 here and in post #2 here.
The Alexis is somewhat “in between” a more typical latex/polyfoam hybrid that only has a few inches of latex over the polyfoam and an all latex mattress that doesn’t contain any polyfoam at all since it has 6" of latex in the top two layers (see post #2 here). A forum search on Alexis (you can just click the link) will bring up more comments and feedback about it as well.
This is the only one of the 5 that you would be able to predict reasonably closely how it will feel to you either in your current configuration or with a slightly softer top layer.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart (which would certainly include all the manufacturers or retailers you mentioned) and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
There is also more about the most important parts of the “value” of a mattress purchase in post #13 here which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists (based on all the parts of your personal value equation that are most important to you).
The better options or possibilities I’m aware of in and around the New York City area (subject to making sure that any mattress you are considering meets the quality/value guidelines I linked) are listed in post #2 here but as you mentioned it’s unlikely that you would find another mattress that was an exact match for any of the mattresses you mentioned in your post so while some local testing on different mattresses may give you some very general ideas about the type and combinations of materials that you tend to prefer … it wouldn’t tell you about whether any of the mattresses you are considering would be a good “match” for you in terms of PPP.
Phoenix.