Hi Runnerjess,
The first place I would start your research is the tutorial post here which has all the basic information, steps, and guidelines that you will need to make the most suitable and best possible quality/value choices … and avoid the worst ones.
The first step in evaluating any mattress in terms of its quality and durability is to make sure you know the quality of all the layers and materials inside it. This means knowing the density of all the polyfoam and memory foam layers. Without this there is no way to know any weak links in a mattress or make meaningful comparisons with other mattresses. I would avoid any mattress where the retailer or manufacturer either can’t or won’t provide this to you.
Post #4 here and the links it includes has more information and feedback about Dynasty mattresses.
I would also read post #2 here and the links inside it before considering any Night Therapy mattress.
Phoenix