Hey Nucro,
Although I do not know the statistics of how many 1.6A P4's can reach 2.1 with minimal or no boost in core voltage, I have chosen the more aggresive route of building a 1.8A system with the intent of driving it to 2.4. Based on my research, I have chosen the ASUS P4T-E and the newer Samsung RIMMS. Yes, like your self, I hope to push the FSB to 133 and run the memory at 1066.
I should have some results within a week, and will share them with the forum.
Toast