Thanks. So this means I have to do the custom vBios file whatever that means, to get it working right? Is this tough to do or simple? And how do OS updates affect the card? I can worry about overclocking it later.
So the starter of this thread, emjay96, actually said his BruceX was 27 sec on 280x but only 23 sec on his 970. And referencing other early posters, Ainth was getting 19 sec on his a 980. But these results are over a year old now. "Justly" does 17 sec on a 280x etc.
So it looks like some people do better on 280x, others better on 970 or a little bit slower than the 280x, and the results do seems mostly in the same ballpark even if one card lags the other. This makes me think I would have a lower hassle experience with a 970 and still do well if I decide to edit in FCP. Maybe I should return the 280x I bought and just get a 970. It is more expensive though.