The x1600 is equivalent to the 6600GT but the GT has been out for a couple years now and offer the same performance.
Are you serious?? x1600 can kill a 6600GT. X1600 have higher clock speeds and more pipelines than 6600GT. But you're right, y ou can't copare X1600 to a X850XT, cuz the 850XT will make a mockery of the X1600.