What speed should you run the memory at for max performance

[Geffen]

I've just brought a Pentium Duel Core E2180 and when overclocking i'm not sure what speed i should be running the memory at. Should i be trying to keep it at the twice speed of the front side bus or just aim to run it as fast as possible. Reason i ask is my memory rated at 1000mhz but the front side i'm only runing at between 250mhz and 300mhz, so i've got lots of head room to clock the ram faster and i'm not sure if that will increase performance or slow it down.