]Go with an AMD build... good value for money. I've seen A10 or FX bundles (CPU + motherboard) for around $200. 8GB of RAM ought to be quite cheap. Same goes for a decent 600W PSU.
You will need to add more money for a videocard capable of playing games at full graphic options, though the listed games are not too demanding. Look for a Tahiti LE-version AMD 7870, provides almost the same performance of a 7950 for ~$220 on sale. Here's a sample loadout. There is a $20 MIR on the videocard and $10 on the PSU. Comes in around $500 but it will last for a while. You can go cheaper by going with a lesser videocard, say a GTX650Ti around $140.
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EDIT: In case it is hard to see:
NCIX Bundle Deal AMD A10-5800K APU Quad Core & ASUS F2A55-M-LE mATX A55 HDMI Motherboard
Kingston KHX1600C9D3B1K2/8GX 8GB Kit 2X4GB 1600MHz DDR3 240PIN DIMM Unbuff Hmp HyperX CL9
Thermaltake TR2 700w Cable Management ATX12V V2.3 24PIN Power Supply With 120mm Fan
Powercolor Radeon HD 7870 PCS+ MYST.(TAHITI LE) 2GB 6Gbps GDDR5 DVI HDMI 2XMINIDP PCI-E Video Card