Hi terrieb,
As you probably know Fox Mattress is one of the members of this site which means that I think very highly of them (and Rick the owner) and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. They would certainly be well worth a visit for anyone that is looking for a new mattress that is within reasonable driving distance.
In most cases and for "most people … careful testing using the testing guidelines in the tutorial and spending 15 - 20 minutes on a mattress can come close enough to predicting your actual sleeping experience that only minor fine tuning would be necessary if any is necessary at all (see post #4 here). Of course this would be true for “most people” but not for “all people”. There is always some additional risk with an online choice where you haven’t tested the mattress in person or the mattress is different from a specific design that you have tested locally but return and exchange options can lower the risk of online choices. There is more about the different ways to choose a mattress (either locally or online) that is the most suitable “match” for your specific needs and preferences and how to identify and minimize the risks of making a choice that doesn’t turn out as well as you hoped for that are involved in each of them in post #2 here.
Phoenix