depends on what they mean by top performance. It sounds like it should tighten up the memory timings which could make your pc a tiny bit quicker. Alternatively it could make it unstable. My guess is you won't notice any difference.
On mine once I switched to 'performance settings' in bios, and it made it slower cos it dropped the fsb from 133 down to 100mhz!
Personally I'd say if it's working then don't go messing about in the bios