Hi mg517,
Those are the specs you need … I think 
My only caution is that you listed a single layer of memory foam and the description says it has 3 progressive layers of memory foam so the 4 lb density may not apply to all of them.
The 4 lb memory foam is medium density/quality and can work well for someone that isn’t in a heavier than average weight range. The 1.5 lb polyfoam (the 44 is a firmness rating which is very firm) is a little on the low density side and I would prefer 1.8 lb and higher because of the greater durability. Once again it would probably be OK as long as you aren’t in a heavier weight range or don’t spend too much time sitting on the edge or your mattress. You can see some of my thoughts about edge support for an innerspring in post #2 here.
The “value” of a mattress purchase depends on how it compares to your other “final choices” and what else is available to you in your area but as a point of reference for a mainstream mattress the Serta iSeries Jubilance has many similarities (4" of memory foam over a pocket coil with a foam surround) except the top 2" of memory foam are slightly higher density (5 lb). Of course it may also have a completely different “feel” that may or may not be suitable for you in terms of PPP because of differences between the springs and the properties of the different types of memory foam so quality comparisons are only part of the picture and comparisons based on PPP are just as important.
Phoenix