One other possible change: Graphics cards based on Nvidia's GTX 680 GPU are in short supply currently, but you can easily find an AMD Radeon HD 7970 for about $480. It's nearly as fast and just a tad noisier, and it consumes only a little more power.
Still, I'd be loath to give up this nifty LGA 2011 system. LGA 2011 will live beyond the current Sandy Bridge Extreme and support a future Ivy Bridge-based CPU, so it still has some growth potential. And even if LGA 2011 never sees an upgrade, it should handle today's PC games and future titles with aplomb. Build it into a system such as the one shown here, and you can play games at any hour of the day or night without waking relatives or roommates, or racking up a huge electricity bill. Good luck!