The out of the box performance of Asus' TOP edition is only marginally faster than a stock GTX 460 768MB.
Obviously with the overclocking headroom in the chip and with that improved cooler design you can hit the same speeds as the stock 1GB card, but then that card can be pushed even further again.
With a simple overclock the 1GB card can be pushed to the sort of speeds the GTX 470 can achieve.
DirectX 11 Performance (2560x1600)
DirectX 11 Performance
DirectX 10 Performance