Corsair XMS2-5400 vs. XMS2-6400

Ok hey guys,

I initially picked out the XMS2-5400 as seen here:

http://www.newegg.com/Product/Product.asp?Item=N82E16820145015

To go with an ASUS P5W DH Deluxe and an D805 CPU.

But then I saw the XMS2-6400 as seen here:

http://www.newegg.com/Product/Product.asp?Item=N82E16820145034

And thought "Oh snap!" I don't wanna shoot myself in the foot by limiting myself on the RAM, will spilling the extra cash for the 6400 be better for me?

Advice that doesn't have anything to do with "Conroe this, Conroe that" is appreciated!

Thanks.