First of all, the cable *cannot* be used as an extension, it is plugged directly into the PSU. Additionally, using cables from other PSU manufacturers is very dangerous as the pins may be different. As far as I know, Asus and Corsair are from different manufacturers, so don't!

I would also advise against it. I had a Corsair power supply with fully modular cables from Corsair and at some point it didn't have enough power, so I simply ordered a Seasonic because the Corsair ones were not available. I assumed that this would be standardised, but beware: the plugs fit at first, but when you take a closer look, the cables are pinned completely differently - in the worst case, the whole mill will smoke off.