Hi adamski,
You certainly have some great options available to you in the Phoenix area (you can see the Phoenix list here). Several of them are members of this site which means that I think highly of them and I believe that they all compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency,
I would focus more on comparing the “value” of specific mattresses since you are buying a mattress not the business itself. There is more information about the 3 most important parts of the “value” of a mattress purchase in post #13 here which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on suitability, durability, and all the other parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase to fine tune the mattress or the exchange return options that are available to you).
I’m assuming that you’ve read the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps most importantly know how and why to avoid the worst ones.
Once you have decided on the types of mattresses you are most interested in testing (see this article) and on your budget (see this article) then I would check the websites of the retailers/manufacturers on the list or call and talk with them in person to see which of them carry the types of mattresses that you are interested in testing that are inside your budget range so you can decide which ones to visit in person.
Phoenix