There are bios updates available for you to turn a reference card into the "ghz" edition. Here is a link for one example: bios update
Do some reading and see whether you think it is worth it. There are plenty of other articles. The bios update takes 2 min, and you get the performance of the ghz edition. Im not sure if the PCS version has a dual bios switch but if it does, then that is even better as the bios can always be swapped back to the default if any problems arise. I use the xfx 7970 with the upgraded bios. It is a fantastic card. Check out the latest performance tests to see it up against a 680. Up to you, they are both good cards.