https://www.asus.com/Graphics-Cards/GT710-4H-SL-2GD5/
$58
I have absolutely no idea whether it is still good in terms of output because it's a new manufacture so who knows what has been changed, but the architecture of this GPU is Kepler, the one before Maxwell. It's an older GPU but it doesn't use binary firmware blobs which means the driver can be whatever it wants to be in Linux. Might be worth testing out by someone here at that price. It can't be me because I don't have a PC with slots.