Definitely the Q6600. All the C2Extreme chips are A LOT more expensive than the Q6600 (more than the $300 difference you anticipated) It is also better at balancing processor loads.

Re: x64bit OS and 8gb ram, perhaps Jafula should look at his resource monitor, because thius topic has been disccussed dozens, if not hundreds of time; WoW is a 32-bit applications and runs through a process called Windows-on-Windows, which is a 32bit emulator. This is the only reason Warcraft will even function on Vistax64, but the side effect is WoW, even multiple instances of it, are still subject to the 4gb cap that XP users are all too familiar with. 4gb is enough for todays version of WoW.

A single GTX 280 card should provide ridiculous performance on any machine running WoW.