Hi JohnOH,
Actually this mattress has very good specs which use similar quality layers to the Tempurpedic HD series with 5 lb memory foam, 8 lb memory foam, and a high quality polyfoam base layer. I would consider all these layers to be good quality. Don’t forget that polyfoam comes in a lower density range than memory foam so the density of each is not comparable.
Just as a comment … the Dreamfoam mattresses are certainly good quality and value but if you are considering the memory foam version I would be very hesitant to use 4 lb memory foams at your weight. latex on the other hand in the right firmness level … particularly if you are looking at the latex versions with more than one layer of latex … would be a much better and more durable choice IMO. At your weight … I would be strongly leaning towards memory foam with a minimum of 5 lb density (like the OMF mattress you tested).
With 4 lb memory foams I would think no. with your weight … I would strongly lean towards higher density memory foams.
They have said that the 13" gel memory foam mattress is just a bit firmer than the Tempurpedic Cloud Luxe which is the softest mattress in the Tempurpedic lineup. In other words … more soft than firm (you could test the Cloud Luxe to get an approximate sense of what this mattress feels like).
I think your budget is too low for the quality of foam and the type of design you will likely need or do best with. Higher density memory foam is more costly than lower density memory foam and the same is true for higher density base layers. I would also think that you may do better with more than just a basic 3" or so of memory foam over a firmer polyfoam base layer and a transition layer in between that uses either memory foam or latex would also be a good idea at your weight. These would both put you in a significantly higher budget in Cal King than the $400 - $500 you are looking at. I just don’ think you will find a suitable memory foam mattress at this price. I would start locally to gain some experience on different types of mattresses (following the steps in post #1 here) and then compare your local “finalists” to online choices to see which direction is the best “match” for your personal value equation. Some of the better options in and around the Columbus area I’m aware of are listed in post #2 here. Some of the better quality/value online memory foam manufacturers or retailers I’m aware of are listed in post #12 here.
I would normally go with the base suggested by the manufacturer you are buying from but in this case I don’t think they have Cal King available on their site). If you do decide to go with the wire grid type of platform like the one you linked … I would tend to use one of the ones with more wires than the one you linked which would provide a more evenly supportive surface … especially with your higher weight. The one you linked would probably be “OK” for a mattress that had a polyfoam base layer but I would tend towards a version that was more evenly supportive. The foundation thread here has more information and links to some good quality and value foundations.
Hope this helps
Phoenix