Most cases, no need to spend over $350 on a CPU. GPU's at high resolution don't need a killer CPU. The only reason you would need a hexacore monster is if you are running a GTX 690 in SLI, Geforce Titan or again in SLI. Even then, there is no point because framerates would be so retardedly high, most 60hz monitors will be limited by their refresh rate. Even 120hz monitors will have trouble refreshing that kind of power. Sandy Bridge is not a bad CPU. Ivy Bridge has no benefit over Sandy other than stock clock temperatures and maybe a 1-2% improvement per clock. I recommend 8gb ram and even that is more than enough. I would move to 16-32gb if you want to implement ramdisk which most people don't know about anyways. I even say go Windows 8 and learn the new OS. It plays games the same and even uses Windows 7 drivers. It's the same thing when Vista was basically renamed to 7 and some optimizations to the kernel were made. 8 just has a different wrapper. An off the cuff build for 1080P gaming that will be great for 90% of the games out...

750 watt PSU (Silver or Gold rating)
Core I7 3570k or 3770k
Any socket LGA 1155 board with sata 6g, usb 3.0, 2 or more pci express lanes, and over $200
A single gtx 680, or for about $300 more, two gtx 670's
Use a heatsink that costs $50 or more, for the love of God, please don't use the stock Intel HSF, it's terrible

This would probably run $1500-$2,000 and will play anything at the highest quality settings. I don't want to pick motherboard brands because there are plenty of good ones. AMD Radeons are perfectly fine. Driver issues with their crossfire are common though.