Here is my build.
http://www.adamroberts.net/blog/davinci ... sh-part-1/
More than capable for 2K and 4K (was playing back graded footage from the BMPC4K at 24fps without issue)
If you don't need Thunderbolt you could go with a cheaper mother board of even look at the Socket 1150 motherboards tho they are a little more complex to get running as a Hackintosh.
The Z77 has been replaced by Z87 now. So you could look at those boards if you can't find the Z77 board I used.
If you are only work in HD you could save some money on the GPUs by going with a 2GB GTX and a GT640 for GUI.
The build you have listed should work fine.