stock performance is probably within about 5% margin of difference between the two in most things
the kt600 is a solid solution and basically represents what via shoulda released in the kt400
the oc potential of the kt600 is limited tho (atleast for fsb overclocking) because of the pci dividers
the memory controller on the athlon via chipsets has also always seemed to have pretty low latencies, and this seems to show in applications that don't need a whole lot of memory bandwidth and instead rely on quick response of the memory subsystem
i think the kt600 boards seemed to max out between 210 and the upper 22x
wheras the nforce2 gets over 230 and 240 with good memory
if you can get a kt600 for atleast 20 or 30 bucks cheaper and you don't plan on doing insane overclocking of the fsb then you'd probably be happy with the purchase
i recommend the abit boards either way you go for socket A
they seem to be very good, like the old days
