I have the 832 which is pretty much the same case. I'm using 6 fans
front - in
top & back - out
two side panel toward the front of the case - in
lower side panel toward the back of the case - out
The upper side back spot is empty to fit my Ultra 120 Extreme
This setup works good for me because I have a 8800GT and the two lower side fans are directly next to it so the one toward the front is sucking cool air toward it's intake and the lower rear is removing it's hot exaust.
With 4 fans I would use the front, top, back and lower front side. Keep in mind that the case is basically a big screen so be mindful of the dB level of the fans because unlike some cases with noise dampening there is nothing to quiet them down.