Great article, and they are beautiful plants - and so varied.
Do you happen to know if any of those cultivars are edible? I have been looking for an interesting looking amaranth that is edible, but it never seems to say whether they are. Apparently the 'seeds' make great porridge, and can be ground for flour or used in bread otherwise. I'd just like to try and see what they taste like.
I don't know of any varieties that *aren't* edible, if that helps. Not only are the seeds edible, but the leaves can be cooked much like spinach. The entire plant is safe to eat, though I don't know of any specific uses for the stems or roots.
I did find several recipes using amaranthus seeds and plants, just by doing a google search on amaranthus + edible.