I got a new PSU: Enermax Noisetaker 470W, with 2 fans and a control knob on back where on/off switch is. The PSU goes at the top back of my case. Do I put it in with the 2nd fan facing the bottom of my case? If I do this then the control knob hi/low lable is upside down? That doesn't really matter but it makes me wonder if I should flip it so the fan is at the top. But then there isn't an exhaust opening in the top of my case. Which do I do?