Hi MLSly,
As you mentioned the harmony is very similar to the Sealy Inspiration in terms of foam density and design (both use 3.7 lb gel memory foam in the top 2" and another 3" of 4 lb memory foam underneath that over a 6" polyfoam base) so I’m glad that you were able to use the Inspiration as a reference point.
The foundation thread here has some suggestions for foundations that would work well for you. I don’t know the specifics of the number of slats in the Sultan Aram so it may be a good idea to get the specifics from Ikea (number and width of the slats and the spacing between them) and then make sure with Novosbed that it would be suitable for your mattress and meet their warranty requirements. If you do a google search on “out of the box foundation” you will also find more sources for the same foundation.
Most importantly … congratulations on your new mattress 
Phoenix