1. upgrade gpu. with matching psu of course if needed.
2. you don't 'need' 16Gb of Ram unless you really do need it. Most games currently don't even come close to requiring 8Gb in a system.
3. Forget huge HDD's. They are uber expensive, and of little use to the public. Much better to get 2 or 3 1Tb-2Tb HDD's for storage, and an SSD 120Gb-256Gb for a boot/primary.
4. a i7-3770k is up to you, since mobo will support it, but there's nothing I can't do and do quite well with my i5. I'm not a BF4 multiplayer or WatchDogs fanatic with a need to have the ultimate detail and highest fps possible, so again, nothing I can't do with a i5 3570k.