Hi rockscreation16,
Unfortunately … this is pretty much the norm. With a day or two on this site and forum, most people would probably know more than most “typical” mattress salespeople and some of your questions will get some pretty strange looks and/or strange answers … or you will see some eyes starting to glaze over with an implied … huh??? 
The luxe has 4.75" of memory foam and the supreme has 4". While the types of memory foam they use is different (the luxe uses the HD foam under the ES), they both have fairly thick layers of memory foam. The Cloud uses 2.8" of memory foam and would be firmer yet (less isolated from the support layers).
One of the difficulties of memory foam is that it you can sink further into it over the course of the night. This is why no matter what density of memory foam you use … layer thickness is important. I would tend to use thinner layers of memory foam when possible rather than thicker layers. With the Luxe … the thicker layers of memory foam are somewhat “compensated” for by the use of denser foam underneath but there would still be a risk of sinking in too far over the course of the night (or in your case it didn’t take that long).
Don’t forget that this would only relate to memory foam rather than polyfoam or latex. All memory foam is soft once it responds (with differing degrees of softness and response) and the “firmness” you are talking about is partly a “feeling” of the type of memory foam but is more likely to do with the thickness of the memory foam and the support layers underneath and how much you can feel them as well.
Are you sure you mean the cloud? None of the Tempurpedics have any polyfoam above the memory foam and in looking at the Relax the back models I don’t see any of them which have any polyfoam either. I do like some of the materials they are using though (It sounds like their memory foam is Aerus and that they are also using Energia in their Pure Relax mattress which is a very high quality polyfoam which is both soft and durable). Which mattress did you mean that has a polyfoam quilting?
The problem with the old Sealy Springfree line is that they used lower quality latex (blended dunlop with a higher level of SBR than I would prefer) but even worse is the amount of polyfoam they had on top of the latex. The Trade Wind Resort is themost “plush and was the worst and used 4” of soft polyfoam on the top of the mattress so people are really sleeping on the polyfoam not so much the latex. There is 1/2" of latex buried in the polyfoam so the upper layers are 4.5" and then you get to the firmer core layers. Not so good!
Post #12 here has some good options in memory foam that are in the price range. Durability is most closely related to density. Quicker response and other differences between memory foams can be formulated into any density although generally the faster response foams are in the 4 lb density range (meaning that they would be a little less durable than 5 lb memory foams). If you had two good quality foams of the same density but different characteristics … then they would be roughly the same durability but the greater mechanical stress that the “softer” foams allowed may lead to them wearing out a little quicker (in the same way that some people who are heavier and compress a foam more or move more will wear out a foam faster than those who are lighter or move less).
Hope this helps
Phoenix