Overclocking Core 2 Duo with slow RAM

[Money]

u dont need to overclock the memory if you're overclocking your cpu...

[Doc Flabby]

If you have slow ram more processor cache will give u a big performance boost.

Clock Speed isnt the only thing to consider with ram, as response time is just as important.

[Ewan]

I've got a new computer coming next week. Originally I wasn't too interested in overclocking so i just bought cheap RAM to match the FSB of the processor. I have since learned of the Core 2 Duo E6400's great overclocking potential with stock cooling, and was just wondering what the feasibility of overclocking is.
Here are the specs that matter:

Core 2 Duo E6400 (2.13GHz, FSB: 266MHz x 8, Bus speed 1066MHz).
RAM: Kingston 2 x 1GB DDR2 533MHz/PC2-4200 Non-ECC CL4 1.8V Unbuffered Dimm 240 pin

Now, I know normally I would want to run the memory at the same speed as the processor, which it will do at stock speeds. My housemate thinks, but isn't sure that I should still be able to overclock the processor and just have it not synchronous with the memory, but isn't too sure of the feasibility or if there'd be much of a performance hit.

If it helps, mobo: Gigabyte GA-965P-DS3P Socket 775 1333SFB iP965 SATA 8 channel audio ATX

In the long run, I'll probably get some faster RAM (PC2-6400@800MHz) but at the moment that's not something I can afford to do, so was just wondering what I'll be able to do in the meantime.


EDIT: Also I've noticed that the E6420 has just been released, might it be worth returning my E6400 and getting the E6420 instead? It has twice the cache, which is the only difference, and is the same price. I don't really know how much cache affects things.