okay so i got kingston 512mb, 400mhz, and another question. i got my old 256mb/333mhz. so i should have them both, though the new will run at 333mhz., or install new and throw away the old. basically, the question is: more ram at less speed, or less ram faster? 
my shitty rig:
athlon 64 3500+
4gb geil ultra4 800mhz
asus x1650xt