Asus have there own overclocking software, it is on the disc in the box that you got with your new GTX 670 Direct CU II, It is the same as the afterburner from MSI.
Just don't forget you will not get better clock speed then the TOP because the GPU has been bin to your card not the TOP.
When you overclock in SLI watch your volt/temp's because it will fail on the card that is not better GPU.