Overclocking the GF114 should not be a problem, regardless of whether it’s reference or specially designed GTX 560 Ti or GTX 560. Most GTX 560 Ti cards will run stable at 920+MHz. We tested the first GTX 560 so far, Gainward's GTX 560 Phantom. Compared to Gainward GTX 560 Ti, the new card turned out to be a better overclocker.
Gainward’s cooling provides a nice foundation for a healthy overclock and we got the following results. We managed to push the GTX 560 Ti's GPU from 835MHz to 930MHz, and the card remained quiet throughout. GTX 560 Phantom was quiet as well, despite achieving even better OC results - we pushed the GPU to 945MHz.
Noise is not an issue. In fact, this is one of the quietest cards we've tested. Temperatures are within normal limits as well, as you can see from the pictures below.