i see your point i am only saying what i read
although to me it does make sense on most resolutions the 320mb matches the 640mb and generally people that use the res were the 640mb makes a difference ie 1920x1200 are running 24" monitors which normally means they would just have to buy the gtx for full aa and af
as it is much faster than a 640mb
and the reason they are supposedly stopping the 640mb is due to bad sales since the release of the 320mb
but as i said i only read this on a website so it may not be accurate