Will it be more performance productive to upgrade my processor to the newer E8400 Core 2 Duo also at 3.0 Ghz but a faster bus of 1333Mhz
( For the purpose of comparison assume that cost involved in upgrading either are the same )
I am referring to gaming performance, fps, etc.
I game at 1280x1024 setting with settings set to moderately high and get playable fps 30 or higher depending upon the game.
Graphics card update, definitely. While an upgrade at all is unnecessary of course, that's a nice rig you have. 
But the cpu you have is already so effective so that if you were to upgrade the cpu, you will not notice a difference in visuals, or fps. Your current cpu is just too good for there to be any significant improvement. However while the graphics card you have is awesome, I would recommend getting a graphics card upgrade - doing so will give you an extra added 10 fps for crysis, and several times more for other games. However I would suggest buying the new geforce 280 graphics card - it just went under a price cut, and has a 12% to 20% increase over the upgrade for your gpu you have currently chosen, for little, if any at all, extra money than the 9800gtx+. Good luck.
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