Affordable Gaming Rig?

I know the words affordable and gaming rig dont usually go hand in hand, but with Civ 5 and Starcraft on the way, I need a computer that can handle those and maybe more on a tight budget. My budget is 700 firm, it's a fairly pitiful amount but thats what I have to work with. I'm not looking for a mind blowing super fast gaming rig of awesomeness, but one that will allow me to play those games out of the box while also have room to be upgraded. I would like to stick with ddr3 ram, either intel or i3 i5, or amd's new line of processors. A radion sapphire card or one thats around that range would also be nice. Could possibly go up to 800.00, but thats with shipping, tax etc. Thanx guys/girls.