Hi apesanteur,
While there are too many unknowns, variables, and personal preferences involved for anyone to make specific suggestions for a mattress or materials for someone else based on specs (either yours or a mattress) or "theory at a distance (see mattress firmness/comfort levels in post #2 here) … the mattress shopping tutorial here has all the basic information, steps, and guidelines that can help with “how” to make the best possible choice … and know how and why to avoid the worst ones.
Once you get to step 3 then the better options and possibilities I’m aware of in the Toronto area (subject to the guidelines here) are listed in post #1 here.
I’m looking forward to finding out what you end up deciding … and of course any comments or questions you may have along the way
Phoenix