Given the value that is out there ... If I was going to look at a mattress with more than 1" of polyfoam, I would make sure that it was the type of foam that wouldn't create problems down the road AND I would expect to pay far less than most people seem to be paying for these types of mattress. I don't mean to discourage you ... quite the opposite as a matter of fact ... but .....................
If I was going to go in the polyfoam direction, I would get very specific about what they were (you can see some examples in the last 2 links I posted) and be reasonably certain they would do what I wanted them to do in terms of support, comfort, and durability. I would not buy something where I had any doubts. It is much easier to know what you are buying when you are looking at materials that have proven themselves and where their qualities are easier to predict. Springs, latex foam, memory foam, and traditional stuffing materials (horsehair, cotton, wool, feathers etc) fall into this category. HR foam to a lesser degree falls into this category as well but it is much more difficult to know what kind of foam is in your mattress as they will mostly not give you the specific manufacturer so you can do some research into it's quality and characteristics. Most of the poly foams are re-branded with "latest and greatest most wonderful absolute heaven" names to prevent consumers from doing exactly this. Most of them as well have not proven themselves (at least in a positive way) in the real world over time.
Phoenix