that's still crazy that you can go up to +900 on the memory! Mine starts artifacting at +775, with +760 being the highest stable. All GTX 670 and 680s use the same 1500 Mhz hynix chips. The only thing that would help on the Galaxy OC version for the memory is the thin ramsink and extra fan.

I know that Galaxy / KFA2 are binning their GPUs very tightly. Any chip capable of doing 1200 Mhz goes on the dual fan custom design. Then with the triple fan white PCB 680, they are cherry picking all their 1300 MHz GPUs for that. This also means that if you buy the dual fan GTX 680 from galaxy, you won't get a 1300 Mhz capable chip because those are being saved for the triple fan version.