Hi scar4343,
The list of the better online memory foam retailers and manufacturers I’m aware of (including Dreamfoam and Brooklyn Bedding) is in post #12 here. As you probably know … Dreamfoam is one of the members here which means that I think very highly of the quality/value of the mattresses they make and they compete well with the best in the industry.
Some people will sleep warmer on any type of memory foam (gel or otherwise) or even on any softer foam mattress so it’s not really possible to predict for any specific person. Even though most people would be fine … any memory foam mattress (or even gel memory foam) can sleep warmer for some people. There is more about the many factors that can affect sleeping temperature in post #2 here and the posts it links to.
As you suggested, the type of mattress protector you use along with your sheets and bedding can also have a significant effect on sleeping temperature. There is more about the pros and cons of different types of mattress protectors in post #89 here and more about different types of fabrics and sheets in post #7 here and the other posts and topics it links to.
There are too many unknowns, variables, and personal preferences involved for anyone to be able to use a formula or “theory at a distance” to predict which mattress may be best for you (see mattress firmness/comfort levels in post #2 here).
While it’s not possible for someone else to tell you which specific mattress to choose … it’s certainly possible to help with “how” to choose. The most important part of the “value” of a mattress purchase is always how well a mattress matches your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). In the end, only your own personal experience can confirm this.
Outside of the suitability of a mattress … the quality and durability of the materials in the mattress would be the next most important part of deciding which mattress was “best for you”. There is more information about foam quality/density guidelines I would suggest in post #4 here.
Once you are confident about the suitability of a mattress and the quality/density and durability of the materials … then the other parts of your personal value equation that are most important to you (including the price and any return or exchange options) and how they all compare to your other finalists would also be significant parts of the “value” of a mattress purchase and which of your final choices would be the best value for you.
Phoenix