I can't totally vouch for this but it is my understanding that the last two iterations of Ivy Bridge (with video on board) excel somewhat in video decoding/encoding as these subroutines are now native in the CPUs. An Intel engineer told me that these CPUs could actually decode video better than the 4900 series or Xeons without on board video.
I've not tested it on a documented basis, but was very pleased with running the system before installing the nVidia GPU (PPCS5.5).
Alex why didn't you ask that aboutr a week ago when I had a Haswell (I7-4770k) that I had just built? Of course I did not instsall The Dark Cloud version of Adobe Premiere on it.
Premiere Pro CC cannot use Intel graphics for hardware acceleration. In fact it often pukes up all over you just trying to use Intel for the GUI. Best if you have ONLY the AMD or nVidia card running. Unfortunately, the new style of switching graphics often makes it impossible to fully shut down the Intel at the BIOS level, where it's best done.
Premiere Pro CC cannot use Intel graphics for hardware acceleration.
Guess things change pretty fast in Adobe town...