^ You won't require "the best" gaming box possible for what you want to do. In fact, I'd venture so far to say that buying "the best" is an absolute waste of money.....either way in a few years time, a $10,000 box will be outdated just like a $1,200 box. Perhaps not quite as much...but then again, you could have purchased 8 additional $1,200 boxes along the way.
If you want to play a game like WOW with all settings maxed, get a Core i7-2600k, any $400 video card from Nvidia or AMD, and 4GB of RAM and you can set the details on as high as they will go. No reason to spend more than $1500 for what you want to achieve. (Unless, you are doing 2-3 monitors and super high resolutions....and then you might need to go with a crossfire or SLI solution with multiple graphics cards). But if you want to play on 1 monitor and resolutions of 1920x1200...you only need a single video card to do that.