Hi dakota,
The first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and perhaps more importantly know how and why to avoid the worst ones.
Outside of the suitability of a mattress in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) … a mattress is only as good as it’s construction and the quality of the materials inside it regardless of the name of the manufacturer on the label. Most manufacturers including Restonic make lower quality less durable mattresses and higher quality more durable mattresses as well so it depends entirely on the specifics of the mattress and the quality and durability of the materials inside it.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses regardless of the name of the manufacturer that makes it.
There is also more about the many variables that can affect the sleeping temperature of a mattress in post #2 here but as you mentioned memory foam will tend to sleep warmer for many people than other types of foam materials (such as polyfoam or latex foam) that are also used in the comfort layers of a mattress but whether it sleeps to warm for any particular person will also depend on how deeply you sink into a mattress and also on where you are in the “oven to iceberg” range because a mattress that sleeps hot for one person may be fine for someone else.
Once you reach step 3 in the tutorial and you are ready to start testing mattresses if you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of in your area.
Phoenix