So I have a Mac Pro 3.1 That I want to max out. I want to run Catalina, if possible, or Mac OS High Sierra, if that's better. I am not really sure what kind of gpu I want to use though. I've seen a people recomment the NVIDIA GTX 680, which is easy enoguh to flash, however, I also see that the ATI Radeon HD 5870 For Mac Pro is also good, though I don't know if that's compatible with my mac. Those are the 2 I'm going for right now, around the same price. Is there any other gpu you would recommend, or any advice about the two I mentioned?