well, it depends on what you mean by better? if you look at some
benchmarks , you'll see that the nforce2 400 chipset (the one the a7n8x-x uses) generall scores higher than the kt600 (a7v600). both boards will support your ram. as for overclocking, i'm not sure. the a7n8x-x has been a good overclocker for many, haven't heard much on the a7v600 (haven't looked either ).
the main difference is extra features.. the a7v600 adds onboard wifi, sata support, as well as a ADI AD1980 SoundMAX onboard audio with spdif output instead of the realtek alc650 on the a7n8x-x.
i guess you could say the a7n8x-x is more of the performance board, while the a7v600 is the feature rich board.
you can compare the two at the asus site as well
hope that helps