I have been running the Sapphire Pulse RX 580 8GB since last weekend and I am surprised how well it has been working in FCPX. The performance is very good for my needs. Based on export times I would say it is twice as fast as my trusty old HD 7950 card. Also, my timeline can handle 4K footage sooo much better than before, without stuttering. I don't have time for games so I cannot report on that. However, I am getting that "Error gathering PCI information" message in system report. Is there a way to fix that? Thank You P.S.: Many Thanks to this community for all the great information shared on Mac upgrades. --- Post Merged, May 11, 2017 --- One more thing, this card makes Da Vinci Resolve usable all by itself! I could not believe the difference from the 7950. It was really struggling before the switch. Then I checked on the Black Magic Design forum and people report performance on par with the 1080 Ti.