Graphic Card for sure IMO
I have a intel 2.4 quad core 775 very old cpu.
***I had a NVidia 8800gts and could play a lot of games on high settings np, because of the CPU and my raptor HD drives etc.***
When playing this game, I had to have everything on low and could just barely run around in game it was jerking around so bad and my frame rate was 2 and 3 frames a sec. I went and bought a NVidia 770 and did not replace anything else but the card and I can now run on HIGH EVERYTHING. Same 2.4 quad etc I did not change anything but my vid card and went from unplayable to I can handle anything this game wants to dish out.
One followup to this. my card is a pcie 3.0 card. my mother board is still the old 1.0. np at all. card works just fine and the game screams now.
Don't get me wrong - I am not sure how your CPU stacks up against my 2.4 quad if it is lower than mine I would prol do cpu, however that's when you start talking maybe a new board and new memory etc etc. I went with a card first because I plan on building a new computer and I can put this fancy new card in my old out of date system and by in another year before I upgrade. I was just overwhelmed that the game was UNPLAYABLE like 1200 on the full benchmark with every setting turned down unplayable and just by buying this really nice vid card I have no lag at all and I went with desktop high on the benchmark and got over 8500.
Just my 2 cents for what it is worth.