Hi sweetdreams,
It certainly seems that you eliminated all your “worst” choices and narrowed things down to final choices between “good and good” which is of course the main goal of the site. From this point, final choices are all about preferences and the tradeoffs between all the objective, subjective, and intangible factors in every mattress purchase and the parts of your own “personal value equation” that are most important to you. From here you are past the point of making “bad” decisions from the perspective or quality or value ad any of your choices would be good ones.
A few comments.
There are really 3 types of specs. One is “quality specs” which are the specs which determine the quality and durability of a material. I believe this is important for a manufacturer or retailer to disclose. The second is “value” specs which are all about how much of each material are in the mattress or the other components that make up a mattress (such as wool quilting vs synthetic fiber quilting or better quality fabrics in the ticking). These are also important to know. Finally, the third type of specs are the “comfort specs” or the “proprietary design” of a mattress which are all about the firmness or softness of the materials or the specifics of the design which are not necessary to know at all for a local purchase because your body can tell you much more about the PPP (Pressure relief, posture and alignment, or Personal preferences) of a mattress than any “comfort specs”. I would not expect any retailer to disclose these for genuine competitive reasons (although some do anyway).
While 1.9 lb polyfoam in a comfort layer is not in the same quality or durability class as latex (of any type) … it is certainly a high quality polyfoam and is a good quality and durable material compared to the quality of polyfoam that most larger manufacturers use in their mattresses. I would consider this to be high quality material especially in a lower budget mattress although I would still not choose very thick layers of this or even soft latex if it wasn’t necessary. Of course 2.0 lb or higher polyfoam in the base layer is also high quality and would not be a durability issue.
2.5 lb or HR polyfoam is a higher quality material yet and has some properties that are similar to latex … even though I would also not put this in the same quality class as latex either. I would consider this to be a premium foam and a good way to save some money compared to latex with less “tradeoffs” than would be involved in HD polyfoam.
If they were saying it was natural then it probably was and they may not have known what you meant (they may have thought you were asking about the specific formula of the latex). The easiest way is to ask if it has any synthetic latex in it or if it is all natural latex. In many cases if it is blended they may not know the blend … but i would also keep in mind that any type of latex is a high quality material … natural, blended, talalay, or dunlop and that the latex comparisons on the site are relative to each other … not to other materials.
At least it’s clear from the specs that the ecofoam (which is just polyfoam) is less than 2" and given the other materials probably less than 1’ (the ticking and the fibers would also be part of the missing 2") so this would not be significant to me. I normally consider that an inch or so of 'unknown" polyfoam in the quilting is generally not a significant issue in terms of durability. Of course you didn’t like this one as much so this is only a generic comment to provide some insights into making comparisons.
These are all good quality materials as well … just like your other choices. Again … Soy foam is just polyfoam.
It would normally make no difference to me what the regular price of a mattress was because this would not be reflective of it’s real value anyway and I would always make comparisons with other mattresses … not with regular prices. The amount of a discount over a “regular” price is generally meaningless to me.
Having said that … based on the materials in the mattress and on what they are offering to add to the comfort and quilting layers and the ticking it certainly seems like great value to me and on this basis I wouldn’t hesitate to buy it if it “fits” in terms of PPP and your own personal value equation and you are OK with any other restrictions that may go with it (such as any comfort adjustments available, warranty or lack of it, or any other parts of the purchase that may or may not be important to you).
I personally would have no problem putting a latex hybrid mattress on a firm slatted surface where the gaps between the slats were less than 3" and there was good center support to the floor. I would prefer this over a solid surface personally. With a polyfoam base … it would be fine if the slat distance was even wider (polyfoam is not as flexible or elastic as latex and doesn’t have the same tendency to sink into the gaps)
So it seems to me that you had narrowed things down to “all good” choices and none of the mattresses you were considering had any weak links or would have been a “mistake” IMO but it also seems from a quality and value perspective you made the best “value” choice as long as you are comfortable with the firmness level and the overall suitability of the mattress.
Overall … I think you did some great research, made some good comparisons, left some good “tracks” behind for others to follow, and ended up doing very well. Congratulations on your new mattress 
Phoenix