Looks like there are vents in the bottom of the case. Mount the PS fan side down to pull in fresh air from the outside of the case thru the vents in the floor of the case.
NOTE: if your floors are carpeted, be sure the vent in not blocked by the carpet. I just set my computers up on a small piece of wood to avoid blocking the vents...
thanks for the feedback. I do have a carpeted floor, so I'll either get that piece of wood or place the system on my desk.