Hi crazyrhoads,
I would keep in mind that the two most important functions of a mattress are to keep you in good alignment and to relieve pressure in all your sleeping positions over the course of the night. The “showroom feel” of a mattress is more subjective and is a less important part of how well you will sleep because your body can’t “feel” a mattress when you are sleeping.
There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support/alignment” and “comfort/pressure relief” and “feel” and how they interact together.
A mattress that feels “comfortable” in a store may not be a good indication of how well you will sleep on the same mattress over the course of the night which is why careful and objective testing (hopefully using the testing guidelines in the tutorial) can be very important. Careful and objective testing is different from the more limited or more “subjective” testing that most people do when they choose a mattress based on “showroom feel” which in many cases can have a lower chance of success than random chance alone (see this study).
Phoenix