I think that rather than trying to duplicate a specific mattress … a “safer” and much more accurate approach approach is to try to duplicate a certain set of characteristics that you like. In other words I would use the Genius as a “pointer” towards a target (your perfect mattress) rather than as the target itself. These characteristics can be “reached” with different materials rather than trying to duplicate a mattress that is made by a company that includes many unknowns in terms of the materials that they use.
The iComfort Genius has 2" of support foam (this would be polyurethane) over 2.75" of gel memory foam (basically a type of firmer memory foam) over a 6" support base of polyurethane. The problem is that Serta doesn’t release any of the details about the layers they use in terms of quality or softness (or at least very few of them).
To duplicate this … or at least come close … you would need to know the density, support factor, and ILD of the top layer of polyurethane (which Serta doesn’t release), you would need to know the ILD, support factor, and density of the gel foam they use (which Serta doesn’t release but the density is about 5 lbs) and you would need to know the density, support factor, and ILD of the base foam layer (which serta doesn’t release). Without knowing these details about each layer … the mattress can only be duplicated by testing other mattresses until you find one that “feels” the same. The problem with this is that the “feel” will vary from person to person depending on how each person interacts with the mattress layers and is also highly subjective. This would mean trying mattresses one at a time until you found one that felt the same to you (even though it may feel different to someone else that sinks into the mattress differently than you do). Even this would depend on the “accuracy” of a very subjective impression and your memory of it. If you have ever tried to test say 4 or 5 different mattresses in a store one after the other you will know how quickly our memories of the specifics of a particular mattress are lost so what you remember the next day will be even less accurate.
So a better way to find something that fits your “target” (your perfect mattress) is to use more objective standards than the feel of a particular mattress. This means using more objective measurements based on your needs and preferences. This will also allow you to test different materials and layers which may have the same performance but feel differently.
The two main functions of a mattress are pressure relief and spinal alignment. Because these are the most critical they are the most important thing to duplicate in another mattress.
Pressure relief depends on the ability of a mattress to form a cradle that matches your body shape and spread your weight over the surface of the mattress. This is the job of the upper layers of the mattress. Different materials can provide equal pressure relief (for example a softer latex and a high quality memory foam can provide equal pressure relief) even though they may feel very different.
Spinal alignment is the ability of the mattress to “stop” your heavier parts from sinking in too deeply into the mattress so that your spine is aligned in all your sleeping positions (with the same alignment as good standing posture). There are many different types of support layers that can all keep you in good alignment (the iComfort uses firmer polyfoam but innersprings and latex are also good and perhaps even better options in many cases). While any of these may work equally well … they will also feel differently from each other.
After these two main functions or “needs”, everything else is about preferences which is also where the “feel” comes from.
For example using latex or polyfoam in the upper layers of a mattress will result in a more “on” the mattress feel while using memory foam in the upper layers will result in a more “in” the mattress feel. Memory foam will “hold” you in position more while more resilient foams that react faster and are not heat sensitive will make movement easier and conform to new positions faster. Memory foam can also be more motion isolating or energy absorbing than other foams although this is increased when the memory foam in on the top of a mattress rather than a deeper layer and also depends on the other layers of the mattress. Other materials and types of layering also have different motion isolating properties that can approach memory foam.
Polyfoam has a more “dead” feeling as a support layer while latex is springer and an innerspring will be springier yet. These are also preferences of “feel”. Higher quality materials such as some of the better innersprings or latex can also adapt to different sleeping positions better than polyfoam or other lower quality materials.
Another example of “feel” is temperature regulation and breathability. Another in the case of memory foam is the “speed” of reaction and the degree of temperature sensitivity. Examples of other preferences that are not so much about feel but may be important to some are how natural the materials are and the degree of offgassing that they may have. Durability (and the price that goes with more durable materials) are also an important preference.
So some of the “pointers” that you can use the Genius for are …
It seems you like a little bit more “on” the mattress feeling than sleeping directly on memory foam. The Genius points to this because the top two inches are an “instant reacting” polyfoam.
Under this there is 2.75" of firmer than average memory foam (the gel foam). This would roughly translate into a higher density memory foam. This means that even though you like to be more “on” the mattress to some degree, that you also like a little bit of the “slow sinking in” that a deeper layer of memory foam can provide. This would be “in between” having an all fast reacting foam (like latex) in the comfort layers and having an all slower reacting foam (like memory foam) in the comfort layers.
Because the Genius has 2" of firmer foam on top and then has firmer memory foam underneath this … it “points to” you liking a little bit firmer comfort layers overall. The Genius is slightly softer than the firmer insight but firmer than the Revolution and the Prodigy. This would translate into either a similar thickness of similar materials and layering or a slightly thinner layer of softer foam (which would have the firmer support layer underneath it to add a bit to the firmness).
It would also point to an “average” support layer which is most likely the firmness level of the iComfort polyfoam used in the base foam.
It would also point to a preference of good motion isolation (if this was one of the reasons you liked the Genius and were testing it with a partner). there are also different ways to achieve this if this is one of your considerations.
All of this assumes that you were testing the Genius specifically for pressure relief and alignment in all your sleeping positions (your needs) and specifically for various preferences rather than just an overall “feel”.
If this all seems too complex … then the simpler “translation” would be that you seem to like a mattress with a slightly firmer comfort layers, average support, a bit of a slow response feeling that holds you in the mattress and restricts movement a little bit along with some degree of a more “on” the mattress feeling and good motion isolation.
You may or may not like the feeling of a more springy support layer because you also liked the Sealy Captivate mattress which is an innerspring mattress and would have a much different feel than the iComfort polyfoam support core. Putting a gel memory foam topper on the Sealy would also feel very different than the Genius because you would be sleeping directly on the gel foam (firmer memory foam) which has a much different feel than sleeping on a comfort layer that has a more instant reacting polyfoam over the gel memory foam and because the innerspring would feel different from a polyfoam support core.
Besides all of this … the iComfort Genius (and the Sealy) of course is poor value and the prices are high for the quality of materials used.
What I would suggest is that you focus your efforts on some of the better outlets or factory direct manufacturers that are near you. Assuming that you tested the Genius specifically for pressure relief and alignment and not just the overall feel (which means the pointers would be fairly accurate) they will be able to use these “pointers” and help you find a mattress that has the same or better pressure relief, the same or better alignment, and a variety of different “feels”, some of which you may like even better than the Genius. In other words … the “target” that you end up choosing may be better than the Genius in some or all of the qualities that you need and prefer regardless of the materials and layering and the value will certainly be better. They will also help you to understand the different types of materials and how they will affect the durability and longevity of your mattress. Best of all … you won’t be paying a “premium” price for either average or lower quality materials.
Some of the better choices in the Seattle area are in post #2 here.
Hope this helps.