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#11
Intel BOXDB65ALB3 Mobo: $89.99
Intel Core i3-2105: $139.99 This one has the HD 4000 gpu and is only $10 more than the cheapest one.
1x8GBG-Skill Ripjaws X Series DDR3: $58.49. You can get more RAM as you go along (preferably not individually as shipping's expensive).
Grand total: $288.47. And you have plenty of room for expansion.