Great build, Only two-three things. 1st
For $5 you can get the Western Digital Caviar Blue 1TB
which is faster and spacer by 100% for a near 9% more money
Are you sure you want to go with win 8? you can take the win 7 Home premium x64 (or professional for more than 16GB RAM) 3rd
Just give a few bucks more and get a mobo with PCIE 3.0 x8 x8 for future CF or SLI. Asus Z87-A ATX LGA1150
or MSI Z87-G55 ATX LGA1150
will do the job.
edit: As for how i7 4770K vs FX 8350 works with R9 280X (7970):PClab test with 7970 GE Hardwarepal test with 7970GE
But for more accurate benchies, my suggest is to wait for final version of the game
. BF4 Beta is not optimized yet and you can see this from many sites that had great problems running the game with FX 6cores.