The GTX 780 Ti didn't exactly get favourable reviews at the place that generally gives GeForce cards favourable reviews, [H]ardOCP. Here's a quote from them about the GTX 780 Ti vs. the R9-290X:
"When it comes down to bang for the buck, the Radeon R9 290X is offering that in spades. Even the Radeon R9 290 is close to R9 290X performance levels for a lot less expense. If you want the "fastest" video card, it is going to be the GeForce GTX 780 Ti. This cannot be denied, it has the fastest framerate performance, but only by a small margin. If you want to save some cash, and still get the same gameplay experience of the GTX 780 Ti, the Radeon R9 290X will save you $150."
Whole article:
http://www.hardocp.com/article/2013/11/07/nvidia_geforce_gtx_780_ti_video_card_review/8
Maybe it's really the R9-290X you want, but hey, it's your $150 to spend as you wish.