Hi yianni54,
It is almost impossible to exactly “match” one mattress to another when different materials and layers are used. Part of the reason for this is that each different mattress will interact differently with each person so if a different layering system or different materials are used then the feeling will be different.
Having said that … if you match a mattress to your own needs and preferences (as opposed to another mattress) or what I call PPP (Pressure relief, Posture and alignment, and Preferences) then you will likely end up with a mattress that is superior (for you) to the My Side without having to duplicate the materials and specs (which you are trying to avoid anyway).
I think the “best” first step is to find a factory direct outlet or a sleep shop where you can test mattresses which use higher quality materials without having to worry about purchasing “unknown” foam. Some of the better ways to avoid most of the traps and pitfalls of mattress shopping are here.
Some of the better outlets that are near you are in post #4 here.
Unfortunately … most warranties are only there to help with manufacturing defects not with the softening of foam itself. Since the softening of foam is not considered a defect (unless it actually goes beyond the stage of softening and enters the final stage of breakdown where it starts to completely lose it’s integrity and resilience and develops deeper impressions without any weight on the mattress) … warranties have little value in terms of how long a mattress will really last in terms of being suitable for an individual to sleep on comfortably. Knowing the characteristics of different materials and the potential “weakest link” of a mattress can be far more predictive of how long a mattress may last in actual use than any warranty.
Phoenix