Yes, any card that works in OS X, but is not the stock Radeon HD 2600 or GeForce 8800GT.
I'll do this tomorrow for a Radeon HD6870 that works perfectly in Sierra with efi boot screens and for an RX460 that also works perfectly in Sierra but without boot screens. In both cases when I have looked at the logs in Sierra, it has been caused (I think) by a WindowServer crash due to a GL driver bundle. And in the case of the RX460, if I Safe boot, it can get to a desktop that has no acceleration.
I'll also try to that tonight, with either GTX 670 or GTX 970, or maybe both.