I am very close to pulling the trigger on a GTX 260 216core. I was up in the air between this and the 4870 but decided to lean this way. My question is, I see that XFX has a Black Edition clocked at 666 core and 2300 Mem. What are the limits of OCing on stock cooling with these cards? I know my current 8800GTS/512 overclocked an easy 100MHZ on the gpu side. What do these guys do?