Hi weirdpuffy,
A mattress is only as good as the construction and quality of the material that are in it. You can see the guidelines I would use when you are buying a memory foam mattress in post #10 here and the Green Choice memory foam mattress doesn’t meet them which means that I personally would pass on it except in unusual circumstances where I was looking for more of a “throwaway mattress”.
The better options I know of in the Denver area are listed in post #4 here.
Phoenix