Depends on the kind of extra resolution needed. I'm a guy that needs shitloads of FP64, which means 7900 series was probably my card.
I was pulling the trigger on that at $768 so if there were a matching 9000 card with 20GB I wouldn't give a damn about spending $600.
Can't do that anymore and the 9000 series is already a few encroachments with no news on features. I can expect great gaming performance, sure.
Am I going to have less jitter, better calculation on shaders, lightmaps, vertices, physics, 0.1% lows and so on? Your guess is as good as mine.
I don't buy these cards purely for gaming. I buy them for their raster capabilities and creator features. I get them because they're all-in-one.