The 1000 series of ati just means that it has shader model 3.0.
an x800 is better than an x1600...
just b/c the number doubles, doesn't mean that's how the model goes..
So twilight is right.
My suggestion is don't overclock if you really do not know how to. It may give you 10 fps more, but your human eye will not be able to tell the difference, only the cpu will.