Dear Reddit, what's the cheapest box you can build that would allow me to run stuff like MW2 and Starcraft II at default quality settings with a proper framerate?

Notes: I'm not in the US, so please don't use parts from crazy Newegg sales or stuff like that, but instead parts that are good value for money in general. Also, I'd prefer an Nvidia video card if that's possible, but it's not a must.