Hi, does the increase in video ram from 32 to 64 make significant difference in using the PowerBook with external displays such as the ACD 20"? For those of you using the 12" with an external display in clamshell mode, is heat a problem? Does the fan come on most of the time? I am thinking about making the switch from my AL 15" to a 12" + external display setup, but am wary about the heat issue and the fan noise. Any comments/suggestions? TIA.