That graphics card will handle any game out there on super high settings.. I believe it will play Crysis on med/high.. My 7900GT GPU can play Crysis on Low/Med
I have never played WOW, but I believe you will get over 100FPS all the time.. I know even my 7900GT gets excellent FPS in most games. The 9800GTX is maybe too fast for just games like WOW.
I think you should get the Q6600 Quad Core... though your current CPU will handle it. The Q6600 is cheap and excellent... You can't slow it down and Veedubfreak here has his overclocked at 4GHz
If you do decide to get the Quad.. your motherboard may need upgrading..
And as far as cooling goes.. for your CPU just get a TRUE it is the best there is and will keep your CPU running super cool.
TRUE:
Thermalright Ultra 120 Extreme Heatsink Review - FrostyTech.com
Hope that helps