Probably nothing at all. Having adequate air flow going through a case seems to be more of a key to seeing good results at cooling in general. With the 939 build here a Zalman CNPS 9500 for the much higher price still saw ide cpu temps in the 40s when first assembled in an older case that lacked good air flow.
When the case was changed and even now after a year's time the regular temp seen after a day and night of being run plus gaming is 34C. The simple task of moving everything into the better AeroCool case had more to do with seeing temps drop sharply.
One thing to add here is that the Asus model seen at the third link posted there is very much like the Artic Cooling Freezer64 Pro seen at
http://www.xoxide.com/arctic-cooling-freezer-64-pro.html The one seen there is more for Socket 754 and 939 models while the Asus being AM2 compatible it also has the heat tubes and copper base.