Just know it runs hotter and louder than the others. You PSU will be fine with that card.
On the other hand, you could flash the 6950 to a 6970 and it may work. If it doesn't work, you're left with something less than the 480 (but still respectable and better performance than the 560). And if you try the flash, you void any warranty.
I wouldn't bother flashing it for just a one or two fps gain over the 480. Get the 480.
The only thing is there's no degree of certainty that the flash will be successful (unless you're absolutely certain?).
Of course the fans going to kick up when the 480's working hard. Nvidia also has a max temp of the 480 at 105C. So it's going to generate some heat. You don't want this in a case that has poor airflow. Otherwise, if you can deal with the tradeoff of a louder fan for the better performance, the 480 will be a good choice.