What he said. You might also want to consider a fan controller. Thats actually an easy way to hookup multiple fans and control their speed. For example, my NZXT Sentry Mesh Controller can hookup 5 additional fans, All my fans route through this and I can turn them up and down via manual control from the outside (in case they are too loud, or to save power, etc). Some fan controllers also have temp guages, which is nice but they are usually off by several degrees.