Two items worthy of note:
1. Let's not forget, there are 120 Hz monitors.
2. Average frame rates and minimum frame rates are two different things. Crysis played great maxed out on my son's box .....except for the part in the airport tower where minimum frame rates dropped to annoying levels.
As for the OC'ing .....
4.6 Ghz is reasonably obtainable on > 50% of 2500k; 10% will do 4.8 Ghzhttp://hardforum.com/showthread.php?t=1578110
The 570's is the best of the 5xx series if left at it's stock settings. It's VRM is perhaps less beefy than we'd all like as it doesn't tolerate increased voltages very well. The 560 Ti's (900MHz factory OC versions w/ the oversize coolers) on the other hand are very robust when it comes to OC'ing and scale a bit better. Twin 900 MHz 560 Ti's will garner 862 fps in SLI in Guru3D's test suite while the 570's at stock garner 873 fps.
Still, unless you are going to exceed manufacturer's voltage limits, the 570 is a fine card. You can crank it up as long as your case cooling can handle it just be careful not to exceed those stipulated voltage limits as there's not much headroom in the 570.