its cutting way too many corners. if its a budget computer to bare minimum, look into using AMD llano chips, as the integrated graphics in the chips should heavy destroy the onboard graphics on the motherboard.
Usually when someone asks for a gaming PC at this budget, I say get a PS3.
But the games you want aren't supported, and I doubt you could find a pre-built that would do it without compromising something quite vital.
I think your stuck.