Hi!
I will try to make this as short as possible: I have some experience in building hackintosh computers (I built my last one some few months ago) and had the same problem – I wasn’t sure which graphic card to pick. So I figured of I buy the most expensive one it would get the best performance, so I went off and bought NVIDIA GTX780.
Things seemed to work, but there were a few issues – Picture preview didn’t work and Mac OSX’s UI became buggy from time to time and the finally – Premiere CC was running slower than Premiere on Windows – note that my CUDA drivers WERE installed and Premiere WAS using them – triple-checked that..
After doing some research on tonymacosx (the best community ever if I may add), I found out that the lower model actually works better – so instead of buying GTX 780 I should have bought a GTX 770. Why? Well because apparantely 780 has an issue with its chip when used by a Mac OS so OpenCL can’t function properly – and that was the reason why I was having problems.
Bottom line is: buy a GTX 770, install CUDA Drivers and have a blast!