If you want a REALLY fast pre-overclocked GeForce GTX 460 then Point of View might have the answer for you as they are releasing the BEAST. No-no seriously .. it's branded as Beast.
The Beast series are of highest and yield graphics cards and feature stability even beyond the documented clock settings of 855 MHz core clock, 1710 MHz shader clock and 4020 MHz memory clock (1005 MHz Quad Data rate GDDR-5).
All of the POV/TGT GeForce GTX 460