nVidia isn't outright better than AMD, they are very competitive. Also there's no real proof to show that AMD CPU's are better with AMD cards.
nVidia's equivalent of the HD 6950 would be the GTX 560Ti.
Is the price comparison to the 6800 series ok that I could buy the 6800 series? What is comparable tot eh 6800 series, say the 6850 or 6870 in nvidia's standards?
Don't feel like shelling out 250-300 on a 6950