Get a 250GB SSD for $150 instead of a 120GB that you have to worry constantly about space on for $100.
Personally, the performance difference between a GTX 780 and a GTX 780 Ti isn't close to warranting the $200 difference.
EDIT: Sorry, I caught that I necro'd this. I really hate the new forum format. It's hard to find things and recommends dead threads.