Hello Soreback,
In the budget range of the 12" Sleep Innovations sure temp … you are unlikely to find high quality memory foam. It will almost always be 4 lbs or less. When a memory foam does not include density information … it is usually safe to assume that it is lower density and quality.
A few overall guidelines that may help to cut through the confusion of looking for good value in a mattress is in post #6 here https://forum.mattressunderground.com/t/latex-mattress
A few guidelines that may help to cut through the confusion of competing claims about memory foam mattresses are these …
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Never buy a mattress that includes memory foam without knowing who manufactures the memory foam so you can check to make sure that the manufacturer is listed on the Certi-Pur site (or another reliable site that tests memory foam for safety and quality). If the outlet you are looking at doesn’t include this information and/or won’t give it to you with a phone call (or if this information isn’t publicly available) … pass them by. There are too many who do to spend any time here.
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Never buy a mattress that includes memory foam without knowing the density and layering of the memory foam layers. Density is a main indicator of the quality and feel of memory foam while the thickness and layering is a key part of how suitable a certain memory foam mattress may be for your weight, body shape, and sleeping postions. If the outlet you are looking at doesn’t include this information and/or won’t give it to you with a phone call (or if this information isn’t publicly available) … pass them by. There are too many who do to spend any time here.
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Never buy a mattress that includes memory foam without knowing the type and quality of the support layers underneath it (either an innerspring, polyfoam, or latex foam). The support layers play a key role in how well a mattress will keep you in alignment and in the feel, performance, quality, durability, and value of a mattress that uses memory foam in the comfort layers. It is just as important as the memory foam itself. If the outlet you are looking at doesn’t include this information and/or won’t give it to you with a phone call (or if this information isn’t publicly available) … pass them by. There are too many who do to spend any time here.
This will eliminate most of the lower quality memory foam choices and save you a great deal of time which can then be spent looking at or talking to memory foam outlets or mattress manufacturers that are transparent about their materials and knowledgeable about what really makes a memory foam mattress suitable for each individual. Memory foam is just a layer in a mattress and like all comfort layer materials, there is a wide variety of different qualities and types that can significantly change the performance of the mattress. The quality, and layer thicknesses of memory foam and how it interacts with the other (non memory foam) layers of a mattress are much more important than the fact that a mattress contains some kind of memory foam itself.
Innersprings are used as a support core and like all support core materials … they can be good or bad depending on the feel you are looking for and how they interact with the other layers of a mattress to produce a mattress that works for your unique circumstances. There is nothing “wrong” with innersprings as a whole … and like all materials used in a mattress they have advantages and disadvantages. They can be a good choice for a support core for those who are looking for a certain feel or are working within a certain budget where support cores that use a more expensive material with more desirable qualities are out of range.
While memory foam has some unique properties that can make them more risky than other comfort layer materials for those that have back issues … the thickness of the memory foam layers (as thin as posssible is better) and other layers in both the comfort layers and the support layers underneath it can certainly reduce the risk of using memory foam for those who like feeling of sleeping “in” their mattress and the disadvantages of memory foam compared to other materials are not as big an issue.
This article would be a good place to start as it helps to explain the basic functions of a mattress and with this knowledge, the decisions about which comfort layers and which support layers are most suitable and preferable for each individual become much easier.
Information about the different materials used in comfort layers and how they compare can be [url=The basic functions of a mattress - Overview - The Mattress Underground]found here[/url
Information about the different materials used in support layers and how they compare can be found here
Information about how your sleeping positions, weight and body shape, and different preferences can affect your choices can be found here and more individualized guidelines are in the sub pages of this section. For example a rough guideline for the appropriate thickness for a side sleeper is about 3" as a starting point and then go up or down depending on weight and body shape.
Hope this helps and feel free to keep the questions coming 
Phoenix