Yup I should have been clearer, DMF has the right idea.

Ordinarily we'd do mobo FSB limits first (old school), but the presumption is that the Intel chipsets, particuarly your P45 these days can go far beyond RAM or CPU limits anyway.
Normally the RAM part would take quite a bit of time to figure out as well, but setting cas 5 should allow most cas 4 RAM to scale well beyond what your CPU will hit. Of course, confirm this with memtest and at 6x multi to confirm.

So once RAM latency and volts, necessary NBv for those respective FSB settings are in place, then it's pretty smooth sailing: CPU increases will then obviously require more vcore.