Hi Tesasguy,
They are one of the members of the site which means that I think highly of them and that I believe they compete well with the best in the industry. You can see some recent feedback about them in posts #10 to #15 here and a forum search on texas mattress makers (you can just click this) will also bring up more information and feedback about them as well.
A mattress that wasn’t listed on a site wouldn’t worry me in the slightest (and it’s fairly common). Of course with any mattress you are considering I would make sure you do some careful and objective testing to make sure it’s a good match for you in terms of PPP and make sure you know the quality of all the materials inside the mattress (and they are completely transparent about the materials and components in their mattresses).
Phoenix