"We use ATIs respectively NVIDIAs standard power plugs. Asus is unfortunately not following ATIs/NVIDIAs solutions and therefore our plug doesn't fit. You can either cut both plugs and connect the wires correspondingly or you can also get 12 Volt power directly from the PSU. There you have to connect the wires as follows: black with black and red (VGA) with yellow (PSU). The yellow cable from the VGA is an RPM signal, that is not needed."
I'd chop the connectors off leaving plenty of wire to play with on the one you need to use, hen carefully solder the wires.
(I posted this once but it disappeared!!)