I can imagine it is, Shecky Lovejoy. I wish I could afford to get that one, or the nvidia 1080 or Titan, whichever model that is, but I can't afford that right now, what with the exchange rate, shipping, taxes, etc ( I live in Canada) . . All I can say is, in theory it works .I've seen a tweet from a developer showing off a Radeon Vega in an eGPU and installed in a Mac pro, and the model listed was a MacPro 5,1. Since neither of us have Thunderbolt, the eGPU is probably out, but High Sierra should support the card with no real difficulties, but you'd have to wait until the new high-end iMac Pro comes out for the drivers to be finalized, because that's the video card it uses, apparently. And, I'm sure you've heard you can get it with up to 18 cores, tricked out and decked out to the nines, but it'll cost you $13,000 (plus tax, of course) -that's for the top end, money is no object one. I'm sure you know that already....Yeah, power could be an issue, but I'm sure there are ways around that. I haven't tried it in my own Mac Pro 5,1 but if someone's willing to give me one, for free, I'll gladly take it (what? what do you mean not a snowball's chance in....oh, right, got it)
So there you go...8k footage needs a lot of power and bandwidth, tons, in fact. Guess you're going to have to save up...
right? and...here I am with a 2k monitor, no 4k for me, let alone 8k. I don't know if they even make 8k monitors--maybe they do,but I haven't seen one, and I'm 100% sure I can't afford one. Heck, your R9 280X is still more powerful than my Sapphire 7950....
that's all I have, k??
John B