Hi,
Things i would change:
-Western Digital RE4 series are made for enterprise use, such as servers and video surveillance. You will be better with Western Digital Caviar Blue or Caviar Black
-I would definitely add SSD. The OS, Applications, Software, Games and other things will load much faster.
-I would get GTX 770, it has the same performance as the R9 280X, only it is $100 or more cheaper than the R9 280X