Depends on how OC-able the cards are but yes, you can see very big performance increases from OCing. Just FYI there's often an issue when OCing in CF if, for example, you use MSI Afterburner with the option checked to copy the settings to similar cards... You pretty much have to manually adjust each cards clocks separately. It can cause freezing or BSOD if you try both at the same time. (So, overclock 1, select other card, and set it to the same speeds). Easy to check using FurMark or gaming benchmarks that you can download for free.