Dude the r9 290x kicks the GTX 780's butt! I would reccomend you change that. If you do, this is gonna be a kick ass gaming pc.
I've seen some of the benchmarks and it does do better, but at what cost? The temps are extremely high and that thing is as loud as a god damn leaf blower. Whereas I can just get the 780 Classified Edition and overclock it to the point where it does just as well as the R9 290X without the absurd temperatures or noise.