I really would not use two layers of Warm and Natural on a King sized quilt. It will be awfully heavy. I would use wool batting instead.
Some people, especially those who grew up with them, like heavy quilts. As an older woman, I do not like sleeping under anything heavy and I also would find it difficult to move a quilt like that around. My dh would have to wash it, as the added water would make it *really* heavy!