Hi mermla,
The suggestion was to provide a “reference point” because the Prodigy is only slightly softer than the Jubilance although of course they use different types of support system and an innerspring may work better for some people than a polyfoam support system that was just as supportive because they have a different type of response curve. The Prodigy also has slow recovery latex under the memory foam and polyfoam (although it’s only an inch thick) and has 5 lb memory foam on top which for some people can provide more “even” support for the curves of the spine.
There are different versions of softness and firmness depending on whether you are describing the “hand feel” of the mattress, the comfort layers, or the support layers. There is more about this in post #15 here. This is why it’s important to test for pressure relief and alignment specifically and separately rather than for the overall “feel” of the mattress in terms of softness and firmness.
The Genius has 2" of low density polyfoam under the gel memory foam and even though it starts off very firm this is low density and will soften more quickly over time. I would avoid any mattress that had 2" or more of low density materials in the upper layers.
The Insight has the 4 lb gel memory foam directly on top of the firmer base layer so there are no obvious “weak links” in this mattress. It is one of the firmest of the iComfort line so it could make a good choice with a good quality topper to provide some extra softness in the comfort layers which would also increase the durability of the 4lb gel memory foam underneath it.
The insight with a 2" 5 lb memory foam topper would be similar in design to the Savant except the Savant has an additional 1" of low density “comfort” polyfoam in between the gel memory foam and the 5 lb memory foam on the top (which usually isn’t included in most of the descriptions for some reason) which would make it thicker and softer than just the two layers of memory foam by itself. While 1" of lower density materials is inside the guidelines I normally consider to be “acceptable” in terms of durability … I would still prefer a mattress without it unless it is quilted to the cover where the foam is compressed with the quilting which adds to its durability.
Of course the choice of the Insight and a topper would have some risk in terms of choosing the ideal combination if you didn’t test the combination together (unless the topper you buy can be returned for a refund) and could also leave you with the question of what to do with your extra credit and would also require some extra cost for the topper. The advantage of a mattress/topper combination is that the top layers are usually the first to soften and break down and it’s easier and more cost effective to replace just a topper if it softens more quickly than the rest of the mattress (or if your needs and preferences change over time) than it is to replace the entire mattress.
Phoenix