For the best all around CPU for both gaming and video rendering, I would recommend you invest into the Haswell architecture (all-new 1150 socket). Second best choice is to build a Sandy Bridge-E/Ivy Bridge-E platform (both use the same 2011 socket). But, I just can't see myself recommending building an older platform system to someone building a brand new rig today. The onlyreason why I recommend Ivy Bridge-E is solely because the 3930K can be had for less than $400 now that the new 4930K has been released. Both offer six physical cores along with a huge L3 cache and hyperthreading. That means you can process up to 12 command strings simultaneously per clock cycle, IF the software you are running is optimized in such a manner to take advantage of the CPU architecture. And of course, the Sandy Bridge and Ivy Bridge CPUs are 64-bit, so no worries there.
As for the GTX780....it really isn't a great video rendering card per say. Yes, it can do the job. But, not as well as the old Nvidia Fermi GPUs. When Nvidia released the Kepler GPU family, they decided to create two separate GPU architectures; one for gaming platforms and one for workstation platforms. The gaming GPU is known simple as the GeForce family. The workstation GPUs are known as the Tesla family. Both cards are great, but ultimately, neither is as good as the other in performing their primary duties. The Titan graphics card is the answer to your prayers. The Titan card is the only graphics cad in the Nvidia product line-up that is designed for both gaming and workstation duties - hence the $1000 price tag. It comes with 6GB of DDR5 and a completely unlocked (no dormant shaders or units) GK110 GPU. The GK110 variant in the GTX780 just can't compete when it comes to workstation duties. Yes, for gaming duties the GTX780 does just as well and in some cases better and worse (depending on the game) vs. the GTX Titan.
The bottom line is if you plan to build a new system that is designed for BOTH gaming and workstation productivity, the parts to go with are:
CPU: Intel Haswell Core i7 4770K -or- Intel Sandy Bridge-E 3930K -or- Intel Ivy Bridge-E 4930K
GPU: Nvidia GTX Titan