Need advice on selection of RAM for OCed Core 2 Duo build

Hi!

I'm in the process of building a new PC and I'm having trouble deciding what RAM I should get. The new PC will have:

Core 2 Duo E6600
Gigabyte GA-965P-DQ6 Motherboard (Unless a better price/performance offering comes when the Nvidia 590/570 IEs are released)

I'd like to get a modest overclock for the E6600 in the 2.9~3.1GHz range (maybe a bit higher, I'd like to avoid increasing voltages - I'm quite n00bish at overclocking). I plan on having this as my primary system for 3-4 years and the only part I intended on changing is the GPU once or twice during that span. NCIX is having a sale and they have a few pieces I was looking at:

Mushkin EM PC2-6400 CAS5 @ $224.99 CDN
Corsair XMS2 PC-5300 CAS4 @ $214.99 CDN
Mushkin EM PC2-5300 CAS5 @ $179.99 CDN

What I'd like to do is buy the cheapest of the three above that'll let me get away with the overclock I want (unless someone can convince me otherwise, but I'm trying to be cost effective )

Please help! The price of memory everywhere I looked online jumped up last week and I don't want to take a chance on missing out on some possible deals. The sale ends today!!

That's the impression I got look through a bunch of reviews too. I think whether I choose DDR2-800 @ CAS5 or DDR2-667 @CAS-667 the worst I'm looking at is a 5% hit from the premium stuff.

But if I intend to OC up to say, 3GHz, with the 9x multiplier that means my quad-pumped FSB is now running at 333MHz right? So if the memory is double-pumped, then I need DDR-667 for that Overclock, correct? I think this is how it works, but this will be only my 2nd systems built my myself and the 1st I've overclocked so I'm still in the dark a bit...