It looks like there is room for 4 in front 2 in back and 1 in the side for a total of 7x80mm fans (not including the ones in the PSU). If it were me, I would cut out the front for one 120mm - locate it as near to the center bottom front (maybe an inch up from the bottom as possible, cut out the back for one 120mm mounted as close to the bottom of the PSU as possible, and use the side fan location to hook up a duct (see SVC.com) to the CPU. Plug up all the superfluous holes from the stock fan locations, above the PCI slots, etc. I use double layers (more to make the color darker) of the colored Reynolds plastic wrap to cover major areas of superfluous holes.
.bh.
P.S. But if you don't wan't to cut, then looking from the open side use fans: front - lower back, upper front; top rear and side; use lower rear fan mount for CPU duct. Block all unused fan holes etc. as above.
Have yourself a :beer: !