Hi can anyone give me info on ASUS Rampage III Extreme LGA 1366 doing 3-Way SLI w/PhysX = GTX580 tri sli + GTX570 for physx can this board take 4 cards?

Hi if anyone can give me a positive answer ASAP would be grateful. Heres my delema im trying to upgrade 980X RE3 from 6gb (CMT6GX3M3A2000C8) to 12gb x2 (CMT12GX3M3A2000C9) or 24gb (CMP24GX3M6A1600C9), question is can i mix 2x12gb (CMT12GX3M3A2000C9) ...