Ahhh
You speak of the FSB...
So, your choices are between a 2.1Ghz T6670, 2.26Ghz P7570, 2.4Ghz P8600, 2.53Ghz P8700 or 2.66Ghz T9550.
Personally, considering the price jumps between the different CPUs, I would stick with the stock T6670.
Unless you are looking at doing some CPU intensive tasks, it will feel just as fast as the more expensive options.