Make sure you match up the outputs to the official Mac version of the HD 7950. (I recently picked up two 7770 for $50 each and one 7870 for $100 with this in mind.) The Radeon HD 7770, 7850, or 7870 run for well under $100 (or the 7970 / R9 280X for between $100 and $200) and use the netkas scripts to add EFI to the ROM.
Only two six-pin booster power cables required. The Radeon HD 7950 ($100-ish) is VERY EASY to flash with the official ROM so long as you get a card that matches the official Mac version (two mini-DP, one HDMI, and one DVI output). The NVS 510 ($50-ish) works and provides four mini-DP outputs. I have bought way too many graphics cards lately^. I have a Mac Pro Mid 2010 running high Sierra, but the graphic card is not compatible with some audio plugins, I need the cheapest one so I can run my stuff smoothly without seeing a black GUI! Thanks 😊
