Hi mike7,
You can see some comments about Diamond Mattress in post #2 here and the posts it links to and a forum search on Diamond Mattress (you can just click this) will bring up many more comments and feedback about them as well (although some of them may be linked to a different Diamond Mattress in Utah or a product with Diamond in the name instead of the Diamond mattress in California).
Of course the best choice of materials and the design of a mattress that is best for you in terms of PPP would always be based on your personal testing or experience and each person can experience the same mattress very differently but you are right that a wool quilting layer above memory foam will affect the feel and performance of the memory foam (see post #12 here). Memory foam above an innerspring support core will also affect the “feel” and response of a mattress compared to a stiffer less springy polyfoam base layer even if both of them are good quality.
Phoenix