I don't know why people say that opterons overclock higher then toledo X2 cores. It's just that the low-end opterons can reach the same oc's as the other higher-end cpus so it makes sense that if your sure your going to overclock it is better to the opty 165
Stock speed: X2 > Opteron (X2 wins)
Overclocking: X2 = Opteron (tie)
Price range: X2 > Opteron (Opteron wins)
Basicly it comes down to this: If your not overclocking the X2 is the better choice and it still can overclock very well if you decide to later on, but if your sure your going to overclock the opteron is better becuase it is cheaper.