Quad Core and DDR2 Overclocking

[Voltage]

Hi,

I have just purchased:-

6600 Quadcore
Evga 680i Motherboard
4x1gig Corsair Dominator DDR2
8800gtx
150gb WD Raptor
X-FI Fatal1ty

Zalman Restorator 2 H20 Cooled on CPU

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Now im new to overclocking DDR2 and quad core so what kind of voltages are acceptable to put through them?

Any advice on overclocking this config? Currently on 2.67ghz