The statement that "wow does a lot of graphics on the cpu" is a meaningless comment. WoW does experience bottlenecks on lower-end CPUs in 5-box situations but your Q6600 is known to be a stellar performer with a good graphics card in it. Any number of folks (me included) have zero issues with that CPU, so ignore CPU for now. (The exception is if you haven't yet set your wows up to use either all 4 cores or dedicated 2 to the first two and 3 to the second two cores. If you leave 'em at defaults, the system will only use the first two cores.)

Your graphics card is roughly equivalent to an NVidia 9600GS, which is a sucktastic card for multiboxing WoW. Upgrade to a 9800GT/GTX series, NVidia GTX260 series or an ATI 4870 series, or better, depending on how much money you want to spend (all of those are under $200). I run 4 WoWs on a 9600GT 256mb card with a Q6600 at 2.4GHz and it runs like a champ.

Your PSU will have to go but you knew that already. Otherwise you're fine.