16Gb of memory isn't necessary. 8gb is more than enough.
Depending on what games you are playing, 780Ti is way more than you need. Its only necessary if you will be playing newer games, like far cry 3/4, battlefield, crysis 3, etc. and thats at max settings. You could save a few hundred and get a 780 or a 770.
If you are using more than 1 TB right now, then 2TB is the way to go, but with Western Digital. Heard Seagate has some issues. If you currently don't use close to 1tb, then there is no need for anything more than that, especially with a 240gb ssd.