Hi Raphy,
I would keep in mind that with polyfoam and memory foam density is a measurement of quality and durability not of firmness. In other words … for these two types of foam … density is a “quality specification” and firmness is a “comfort specification”. Any density of polyfoam and memory foam can come in a wide range of firmness levels. With latex it’s different and the density of the foam changes with firmness levels so density is more of a “comfort spec” with latex not a quality spec.
All memory foam and polyfoam is mostly made from petrochemicals. The closest to an “all natural” foam material would be 100% natural Talalay or Dunlop latex that don’t use any synthetic rubber in their formula but even with these there will be a small percentage of other substances used to make the foamed latex core (see post #8 here).
You are very fortunate to be in the Montreal area because you have many local manufacturers and some great options available to you. The better options and possibilities I’m aware of there are listed in post #276 here.
A forum search on Montreal (you can just click this) will also bring up more information and feedback from other forum members in the area.
Phoenix