Hi rktrump,
I think the only way I know to make sure a foundation fits would be to measure it or have the retailer measure it for you before you buy it to make sure it fits the space. Most king size mattresses and foundations are 76" wide but the one you have now seems to fit so there may be others that fit as well. There is more information about foundations and a number of the wire grid type foundations similar to the one you linked listed in the foundation thread here but as far as I know they are all 76" wide (at least in their widest part) in king size.
The Sultan Edsele is a latex mattress not a memory foam mattress (they are very different) but all foam mattresses generally do best with a strong, non flexing, firm and even support system underneath them (not a box spring which flexes). Slats with gaps 3" or less are ideal for a mattress that has latex in the bottom layer. One of the wire grid types will usually work well also although I would read post #10 here before buying one.