Have there been more benchmark reports about the i7 performance with the external fan? If that is all it takes to prevent significant CPU throttling then it is (to me) a pretty moot concern so long as there isn't damage being done to components when using the fan for long periods of time. Seems like folks are saying the CPU will throttle due to not enough power but other reports say that so long as the temperature sensor is cooled the CPU/GPU runs well.
I wonder if MS was overly sensitive to criticism of heat in the SP3 and set that sensor up to prevent the SP4 from getting "too hot" from a subjective POV even if it limits performance that is otherwise acceptable.
I'm not even sure external fans make any difference at all.
I just ran a POVRay rendering test. The file I use for rendering has resulted in CPU temps maxing out at around 75 degrees C.
Then I ran it with a laptop cooler under the entire bottom of the case, running full blast. It made no difference at all.
What's more, according to HWinfo, there was no thermal throttling evidenced either way. Only power throttling (and the CPU frequency still held steady at ~3100 Mhz).
Granted, this was a CPU-only test, not a CPU plus GPU test. But considering the Tjmax is 100 degrees C, and considering that the SP4 design already seems superb from a cooling standpoint, I have trouble seeing the impact of external cooling.