if u decide on waiting for the 939 a64's , u may wont to wait on buy Ram/Vid/Mobo ect.. since parts get cheaper with time, and u cant put it together witha processor anyway, u may as well buy those parts when u buy the processor.
i didnt research any 64 bourds yet, but the one u linked doesnt use Dual DDR.
the ram is personl preferenc(i guess) ,i'd be just as stisfied with cas3 ram and save the extra bucks... the diff between cas2 and cas3 is prolly only measuable in Micro Seconds or somethingorOther.