Well, I think the verdict is in: it is most definitely a Crinum Lily. To left is my lily, below is a picture from Amaryllids in Cultivation. I don't know what variety this is, but 'Ellen Bosanquet' is very common in Florida and looks a lot like mine. So from this point forward I'm now calling this a Crinum 'Ellen Bosanquet'. (If anyone sees this and determines I'm wrong, please let me know. I'd love more info.) Since this plant has bloomed, I've noticed it frequently in my neighbor's yards, and even a clump in what looks like an abandoned lot. That gives me hope that it will be easy to care for. So far, I'm shocked that these suckers haven't long since died with the care I've given them. Sometimes you spend a lot of time finding the perfect plant, and sometimes the perfect plant just finds you.