[Moved to Hardware forum.]
Start at http://ppbm7.com/index.php/tweakers-page and read all the articles, especially about balanced systems
Then more reading
-3 price level ideas in http://www.pacifier.com/~jtsmith/ADOBE.HTM
-what PC to build http://forums.adobe.com/thread/947698
-2 how to build videos http://forums.adobe.com/thread/1104182
-another video http://forums.adobe.com/thread/1145366
-another video http://forums.adobe.com/thread/1132363
-planning & Building http://ppbm7.com/index.php/intro-part-1
-memory for LGA2011 http://forums.adobe.com/thread/1098759
-an Adobe FAQ http://forums.adobe.com/thread/878520
-several more links http://forums.adobe.com/thread/815798
-build tuning http://ppbm7.com/index.php/final-results
Right now GPU acceleration requires fast CPU processing to push the GPU since the media ahs to decode at the CPU first. So you cant lower the CPU because of the GPU. Those 2 you list would be ideal together. The 770GTX would sit idle far more with only a 4770. Cuda Right now performs better than Open CL so Nvidia is prefered.
Yes unfortunately they didnt do the test with all the Geforce cards as well which would have really shown the CPU processing to GPU processing ratio. They also conclude the codecs decided the differences but dont say the clear reason why which is the entire point to the benchmarking. Decoding/Encoding is done at the CPU and if the codecs are effecting the performance of the GPU's then that means the CPU's are deciding the performance of the GPU processing. That needs to be stated.