The video card has the best cooling system there is, cool, quiet, and fast. The case has a side fan to keep that video card cool. Later on you can add a SSD to speed up boot times and program loading times, but with this limited budget, it's best to get the needed items first.
I like that build, I'd still pick the R9 290 and an SSD for the price but if you want the GTX 780 then nothing wrong with your route, that build will max every game you throw at it with no issues.