I found other source where they said it's around 1200 bogomips for a single core. That would means that you only need 5 times more core which is far from being an issue, 100 cores, which means only 25 processors.
Yes, but considering that newer CPUs do not have increasing frequencies, I guess you are more or less doomed to scale horizontally, and not vertically anymore.
However if you want one fast core, you're screwed :)