Hi aoysgelt,
This wouldn’t be an exact comparison because the two sleeping systems would end up being different even though the layers were somewhat similar. A topper for example isn’t quite the same in feel and performance as a layer in a mattress and differences in ticking can also make a difference. The differences in foam types and ILD’s may also make them quite different. The advantage of the Regalis is that it, and their other models, are designed to be very similar to the equivalent Tempurpedics (and they have actually worked on making them comparable in feel and use their retail “bricks and mortar” outlet to fine tune the legitimacy of the comparisons they make) and because of this … you could test a similar mattress by testing the Tempurpedic to see how it interacts with your body type and sleeping style.
The Regalis as you mentioned is
1.8" of 8 lb memory foam
2.2" of 5.3 lb memory foam
8" base layer of HD polyfoam (2.1 lbs)
Total cost = $1599
The Sleepwarehouse.com would be
3" Sensus 5lb Memory Foam or 3" Aerus 4lb Memory Foam
2" HR 1.8 lb 28 ILD Premium Base Foam
2" HR 1.8 lb 32 ILD Premium Base Foam
3" HR 1.8 lb 40 ILD Premium Base Foam
$799
2" Venus 8 lb topper = $644 (including topper cover)
Total = $1443
Total difference = $156.
As a point of reference … Rocky Mountain Mattress also offers…
3 inch layer of 5lb. Sensus brand memory foam
Two 3 inch layers of interchangeable high-density Reflex foam in the core
$745
2" Venus 8 lb topper = $555 (including topper cover)
5% “The Mattress Underground” discount = $65
For a total of $1235
Total difference = $364
Of course these are all different mattresses with slightly different foams and covers and layering (although the memory foam in option 2 and 3 are the same) and the base layer in the Select Foam is higher quality/density and it is more of a known quantity (you can test a widely available mattress to get a picture of how it feels and performs) but you’ve correctly identified the advantages and disadvantages of each choice.
You have choices between “good and good” which is the best place to be and the differences are more about your preferences and the pluses and minuses of different designs and their importance to you than they are about one being “better” than another.
One final note I should mention is that Select foam is also about to be listed as a member here so letting them know that you are a member of The Mattress Underground, if you do decide to go in that direction, will give you a 5% discount there as well.
NOTE ADDED: Select foam used to be a member of this site but because of ongoing customer service issues and delays their membership was terminated and I would read the warning here before considering them.
Hope this helps.
Phoenix