the memory is only rated at 1000 MHz, so anything over that is just luck of the draw. the good news for you is that a bigger memory OC probably won't increase your card's performance at all; they already have plenty of memory bandwidth.

iirc, your memory IC's are bare with no heatsinks on them. it wouldn't be a bad idea to put RAMsinks on your memory anyway. whether it helps them OC farther or not doesn't really matter.