Off the top of my head I would say 2100+ because the max multiplier is 14.. if your lucky. Sorry but you should check the ASUS site to verify. You could get a 2500+ and unlock it bring the multiplier down to 14 then kick the FSB to the roof, but that would probably be a waste. I say unlock your 2000+ to increase the multiplier to max and then go nuts with the FSB....
To err is human... to really screw things up you need a computer!