The nvidia specified clocks of a 7600GT is 560/1400. ANything higher that that is overclock[maybe factory overclock or user overide].
The 590/1600 is for the XFX 7600GT XXX verient which they say can beat all other 7600GT in market nd is factory oced. And the lower version has 570/1450. The stock version is with 560/1400.
The XXX veerient is at least 2l more priced than normal. Why waste money for factory oc. Just get one with 560/1400 for sub 11k nd make gud air flow in cab nd shoot it up to some 620 or 630/1600 or somethin.
See. after the oc its the standard on which wins nd all that 3k has been wasted. XFX has not even changed the HSF on XXX version. They should have at least use more efficient HSF.