I am confused please help ???????

hello...!

i have q6600 G0 cpu and OCZ SLI-Ready 4GB Kit DDR2 PC2-6400 memory and asus p5n-t motherboard.i wana change my q6600 to q9650 and then overclock it to 4ghz.so my question is do i have to buy better ram which can go for higher fsb or can i overclock my curent ocz ddr2 800 ram?or do i have to go for PC2-8.500 ddr2 ram so that i shall overclock my new q9650 @ 4ghz on air.my specs are..

q6600@3.0ghz
zalman 9700led
ocz sli ready ddr2-00 ram
asus p5n-t board
xfx gtx260 core 216 tri SLI
corsair tx-850 psu

and i want to change these things

from q6600 to q9650
zalman 9700 led to coolermaster v8
asus p5n-t i think is ok.....
and i am confussed in ram ????

if i have to buy PC2-8.500 ram so which one shall i buy then...?i mean kingston,corsair, ocz reaper,Mushkin xp2 etc,etc.

please help me.....

you can run fsb 400 mhz (1600 for 3.2 at x8 multiplier)