For you, the best advice I've seen so far is the i7-5960X and added RAM, provided your motherboard can take it. For $1000 to double your core count is pretty good, and will make a real difference to your render times for single frames. While the Xeon E5-2670 is cool, at $1500 each that's a $3000 proposition for 32 cores (they're 8 core, 16 thread just like the i7, but they play nicer in pairs... meaning you need a new motherboard as well if you go that route).

If you are looking at an incremantal improvement/upgrade, go the i7. If you want a whole new system, then design for purpose.

I built my system from components, nothing survived of the old box except a single hard drive. Currently I have an i7 hex core 3930k 3.2ghz (12 cores), 64Gb RAM, Windows 7 Pro, ATI 7950 GPU with 3Gb memory. It's 2 years old, almost, and to step up I'd need to start over with a workstation and spend about $6000.