I'd say you should probably lock down your CPU, RAM, and video card before you worry too much about storage. Also, whatever you do, for the love of God make sure you get an SSD, even if it's just for your OS partition. I can never go back to booting off of a mechanical HDD after seeing the light. The Samsung 850 Evo is (or at least was) the gold standard there. Right now I'm running a 320 GB SSD coupled with a 3 TB HDD for file storage and most of my games, with only the OS and and a few favorite games on the SSD.