overclocking hardware question

hi guys sorry for all the words and stuff but i was talking to a budy of mine who knows a lil about oc not alot but a lil and he told me the memory i have not really that good with oc since its 2 stick's of kingstone value ram and i was wondering knowing how my board supports only 667 pc5300 ram would it be alot better if i get like 2 sticks of 2gb Crucial Ballistix Tracer pc2 6400 or 2 sticks of Crucial Ballistix Tracer pc2 8500 the reasson i ask about this is my budy told me with the board i have which is the asus p5gc-mx/1333 when overclocking my intel core2 duo e8400 processor it up the ram speed and i fingure if i get memory like this it would not put alot of stress on the ram since the speed of the ram.