Hi Moose0721,
Thanks for some great questions 
The information on the site and in the forum comes from many sources. Some of it comes from thousands (literally) of hours of conversations with dozens of mattress manufacturers all around the country who in many cases have made mattresses for decades. They are well aware of the different materials that are available to them and the specs, advantages, and disadvantages of each material.
Part of it comes also from having come to know what you could call “insiders” in the industry who have many years of experience in different parts of the the industry, are well aware of the trends that are happening, and why different manufacturers take the approach they do in manufacturing and pricing their mattresses.
Part of it comes from thousands of hours of research (again literally) into the properties and specs of the different materials that are used in mattresses and what they really do as opposed to what various interests would have people believe they do. There are many technical sources on the internet but they usually involve going much deeper into various searches and then taking the time to read (and understand) some very difficult and technical reading. Sources like patent applications, SEC 10K forms, industry publications and sites, foam manufacturers, and many others are also valuable sources of more accurate information than most people are willing or have the time to pursue.
Part of it also comes from an understanding of how different types of manufacturing techniques and layering patterns interact with each other and with the people sleeping on them. This information too has come from many sources both online and on many hours of conversations.
Part of it come from many many hours of personal testing of mattresses with different types of layering, construction, and materials both by myself and others to “translate” various ideas and knowledge into practical terms.
Sometimes information has to be “figured out” as in some of the specs of the iComfort. I have seen samples of the actual foam used in the iComfort, laid on each model to see how it felt and performed in comparison to other mattresses, talked to many people about the specific foams that are used and what is in them, seen the specs of each mattress which are available at various online outlets, and also had to use various calculations to determine the actual density of the gel memory foam they (and other manufacturers) use.
I typically spend about 16 hours a day and 7 days a week with the different “hats” I wear in building this website and gathering the information on it.
I hope my last answer and the hundreds of pages on this website and on the forum have helped you understand that there is much more than just “minimal facts” behind anything that goes on this website. Canada also has many independent factory direct manufacturers just like the US … however also like in the US there are areas where one of these isn’t within reasonable driving distance. In cases like these … some local mattress testing will certainly give you enough information to create a rough “prototype” for an online order of a high quality and value mattress from a Canadian or American manufacturer. Sometimes this is the best source of quality and value in a mattress purchase and it is available for anyone in North America when a lack of other good choices warrants it.
In terms of durability and longevity … there is no doubt in my mind that the Tempurpedic uses higher quality and more durable materials. Comfort on the other hand is a personal issue that is unique to each individual based on their height, weight distribution, sleeping positions, and preferences and how a specific mattress interacts with their unique needs and specs. Even the worst quality cheapest materials can be used to make a mattress “comfortable” (which is really a meaningless term and very subjective for each individual). The issue is how long will this “comfort” last and did you pay a fair price for the materials and construction used to produce it. This is where the major manufacturers fall short, not in their ability to produce “comfortable” mattresses. Most people who buy a mattress based on subjective factors like “comfort” in the “highly managed” and artificial environment of most mattress showrooms or who focus on brands they are familiar with through advertising will not do well in terms of the value and/or the durability of their purchase.
Major brand mattresses are not all “bad” mattresses … but the best of them do not compare well with many if not most smaller manufacturers who use much higher quality and more durable materials at the same price points.
I personally wouldn’t consider either. Novosbed doesn’t provide the source or any certifications of the memory foam used in the Novosbed which they don’t give on their website and won’t release to customers on a phone call. There is some very bad memory foam used in mattresses that have a 5.3 lb density … and much of it comes from China. At least the CertiPur or other certifications from independent testing groups will help avoid these questionable sources of memory foam.
If you search the web and take a look at some import records that are available you will see shipments to Novosbeds from URE Plastics in China. This is why I normally suggest the four guidelines in post #2 here when buying memory foam. Enough said?
If you were to buy a memory foam mattress like the Novosbed (assuming it was good quality) … then there would be no need to add more memory foam as it would already have enough. Too much memory foam for an individual’s requirements is not a good idea and will increase the likelihood of back issues that come from sleeping out of alignment. With 4" of memory foam and then another 3" of topper … you would have a total of 7" of memory foam. This would not be suitable for anyone.
Thanks again for your great questions and giving me the chance to answer them with more than “minimal facts”
Phoenix
NOTE: Since this was written Novosbed now uses US manufactured foam that is Certipur certified and are completely transparent about the quality/density of the materials in their mattresses and are included in the list of memory foam sources that are among the better quality/value online memory foam options.