Yeh I'd say GTX 770 unless you want to see how far Mantle goes and if you plan on playing a lot of BF4. You might get better fps from 280X in mantle-supported titles, particularly with your 8 core (4 module) CPU.
"Price-wise, the R9 290 is closer in price to the GTX 770 than it is the GTX 780. There is a $70 price difference between the GTX 770 and R9 290. However, compared to the GTX 780, the R9 290 is a whole $100 less expensive than the GeForce GTX 780. Performance-wise, the R9 290 is on par with the GeForce GTX 780. The R9 290 is a much better performer than the GTX 770 or Radeon HD 7970 GHz Edition. The R9 290 is providing the performance of GTX 780, at $100 less cost. The value favors the AMD Radeon R9 290 in an epic way. The Radeon R9 290 provides the most value for single-display gaming on the market today."