why do you want to use the morex and what for? do you have 2 car computers? one of an opus and the other of a morex?
if you just have one, eliminate the morex entirely. remove it from the motherboard and drives and plug the wires from the opus in the respective sockets. an opus makes your old psu redundant in every way. you then need to have 12 volt wires and ignition etc wired to the opus to allow it to turn your pc on and off with your car.
I may be way off track but I'm not sure if you know what your opus is for... or do you just want to use the morex to give 5 volts for some devices or sumthing? I'm stumped