Hi, I was looking for a power supply, around 600 or 700 watts, I planned on having just one better graphics card, two hard drives, about 6 140 led fans and a 250 mm led fan, and 2 DVD drives. So I need to know if I need more than one 12v rail for that, or not, and I would like to know when multiple 12v rails become necessary. Thanks for anything that you can tell me.