well, i got a 9800 non pro, thats doing 400mhz on my 3.3ns ram, im using some pretty big copper ramsinks, and after some time they are getting pretty, hot.
i havent used any voltmods yet, but temperature is becoming a issue after some time at this speed. so i guess that if i could WC the ram i would see at least an improvement in long term stability.
i know that this may not be the info you wanted, but its what i got
PS: if anyone knows how to remove some ramsinks stuck with Arctic Alumina Epoxy plz send me a PM.