Hi Quentin1,
Almost everyone faces a similar choice and you can find some of the guidelines I would use to help you make the choice that is best for you in post #2 here. This may be different from what someone else thinks is best for them because each person can have different ideas about the criteria that are the most important parts of their personal value equation.
Once you have eliminated the worst choices (which you have) then the final choice that is best for YOU depends entirely on all the objective, subjective, and intangible criteria that are most important to you along with how comfortable you are with the added risk of an online purchase.
I don’t recommend what to choose … only how to choose … and all of your choices are between “good and good”. I think highly of Ron at the Mattress Factory and I’m assuming you have talked with SleepEz and Brooklyn Bedding (both of which are invited members of this site) and narrowed your options down to the specific mattress you would choose with all three of them.
As difficult as it is … when you are down to "all good’ options and all of them are better than anything you would find at a mainstream outlet and there are no “clear winners”, then it’s not really possible to make a mistake in terms of quality or value but only you can decide on which of your final three mattress choices is best for you.
Phoenix