well here is my first attempt at a duct mod. I turned my 80mm exaust fan around to make it an intake and used dryer vent duct for the actual duct part. I left my processor fan on it because both fans have an approx. the same CFM rating. Anyway, My temps have only dropped about 1-2 degrees C, but I believe this is partly due to the fact that the intake in the back is close to the hot air exaust of the PSU. I think to make this effective and tubing of some sort will need to be added externally to drop down below the case to extract even cooler air.
Pics:
http://home.insightbb.com/~campbellmb/DSC00037.JPG
Pics:
http://home.insightbb.com/~campbellmb/DSC00037.JPG