In order for you to run your memory at PC3200 speeds (sync), your FSB has to be upped to 200 (400mghz)... At your stock setting of 166, your memory is going to run at 333 (PC2700).
One way to bypass this is to run your memory async, but it isn't as effecient and any higher speeds of the ram is going to be bottlenecked by the system...
Conclusion: Unless you oc your FSB to 200, stick with 2700 settings.