I looked at a nVidia 580. Wow, those are pretty expensive.
I'm currently playing with the idea of rendering arts, and this card performed best on tests, especially for the program Octane.
It's slightly older, harder to find, and I'm aware it was considered overkill of sorts--why? I mean obviously whatever extra it has must be part of the prices being so much higher than, say, a 660 or a 660Ti. I'm aware rarity is a factor also.
But seriously, what is it about a 580 that makes it at least as good if not so much better for rendering than a lot of cards of this generation?