Graphic card replacement options

All the replacements have been discontinued, but you can still find them used and refurbished.

I'm not sure which features are needed for 'compatible configuration' but assuming the following (2x Display Port + DVI output and using at most one of the MP's mini 6-pin auxiliary power ports) gives...

> Another HD 5770 (Mac Edition or PC card flashed with Mac Edition firmware; does not support Mojave)

> Quadro K5000 (Mac Edition cards available; PC cards work without bootscreen but can be flashed with Mac Edition vbios for bootscreen)

> RX 470/570 (Requires MacOS Sierra and newer, no bootscreen)

Relaxing the stated 'compatible configuration' assumptions opens more options.

AMD cards available on eBay which have been modified and are showing support for Apple Boot screens and Metal (for use with Mojave) are mainly the R9 280x series at around US$275 and the much stronger and more expensive RX 580 at around US$650 at this writing.

Or replace with a used 5770 with Boot screen support for about US$150.

do you edit videos?

do you want to install Mojave on this computer in the future?