Novuake :
No no. Other way around, you want the 1100 to go as high as possible BEFORE you OC the VRAM.
OK, this is what i have doen today. I started my oc with 1100 on the core and stock speed on the memory, which is 1250, and +20% power (tanx for the tip). I ran 3d Mark 11. The highest stable oc of the core was 1170, but the highest x-score on 3D Mark 11 was with 1150. After determining the best oc on the core i started the oc on the memory. Strangely the higher i went on the memory the worst my x-score became. So decided to let the memory run at 1250.
Then i started up battlefield 3 with 1150/1250. This resulted in 70-110 gps on ultra, 1920x1080, 120hz. While playing i raised the memory clock to 1350 and the system appeares to be stable. I run a crossfire setup and now my framerate is between 90-130, which is the best fps i have had so far on this rig.