There is an easier way to make a self sufficent power supply. Just take a paperclip and or electrical wire, connect the green wire "port" on the mobo connection to any black "port". Put Electrical tape over it.
Ummm , i want it basicly for just running extra fans that i plan on adding to my case , just reduce the load on my main psu , didnt think it would do anything else , it just sounded like a nifty idea.
Just get a nice big PSU, and you'll be fine. Your fans don't suck up that much power, and if they're not switching fans, the power consumption stays constant.