No need for your CPU fans, just by a regular fan from Wal-mart. I would suggest cutting a circular whole 4" diameter and just putting your fan behind that so the air will circulate threw the back and out the front without even seeing the fan. Keeping a nice cool tempature and no heat problems, a suggestion though, move your tower away from that grow room, roughly 10", your tower will heat the side of the wall, if your computer is garbage of course.