What like the 5870's owning in xfire 150 FPS.....go check the heaven 2 bench out on this board, difference is like 15 FPS between a 480 and 5870, it's not over two times like this bench.
If you look at the side by side comparision as in your own thread
http://forums.overclockers.co.uk/showthread.php?t=18136044
The 480 is most of the time showing approx twice the fps figure compared to the 5870.