Hi mvoeg,
Just in case you haven’t read it yet … the first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that you will need to make the best possible choices … and know how and why to avoid the worst ones (including major brands).
Once you are at step 3 and are ready to start testing mattresses then the better options and possibilities I’m aware of in the Chicago region are listed in posts #2 and #4 here.
Phoenix