For development it’s never overkill to get as much power as possible. At the very least it will improve the speed of building lighting, if you’re creating your 3D assets then you would want it even more.
As far as the parts go, I wouldn’t worry about getting that fast of RAM, just a minimum of 1600mhz
If you don’t need to upgrade immediately and want to go high-end, the Haswell-E processors will be out in the second half of this year and should be a nice upgrade. Otherwise I’d recommend like the i7 4930K instead of the 4770