That looks like a solid build. I don't know about the Corsair SSD, i'm sure someone else can chime in.
As for adding a second 780 in a few years. I can promise you that you won't. In a few year mid range card will most likely beat the 780 with ease.
Thanks, my 2 options are getting a PS4 and a new TV or getting a gaming PC. I was am still not 100% sure but I am now leaning towards my first ever gaming PC (and first PC since 2005).
It sounds like I'll be OK with getting this and it lasting this generation.
I am really concerned the machine I am building won't keep up with next gen hardware (I know my planned PC build is technically better hardware but I am worried that as time goes on and developers get used to the lower level access of the next-gen hardware games will look better on consoles).