What do you mean by "The r9 will Dual Graphics With My CPU"? The FX-6300 has no graphics card of its own unlike AMD APUs and Intel CPUs. The FX-6300 is just a processor, and that's it so there's no dual graphics to be had there unless you buy two R9 280Xs. Anyway, the GTX 770 is a better GPU than the R9 280X by quite a bit and is objectively more powerful. Aside from price, there's really no reason to consider the R9 280X.
Just a warning though; I have the same setup -- an FX-6300 and a GTX 770 -- and it's quite powerful, however there is significant bottlenecking going on depending on the game. The GTX 770 is too much of a beast for the FX-6300 and it's not going to complement such a GPU as well as an i5. That's just something to look out for, but overall you'll see better performance in games that don't result in CPU bottlenecking with the GTX 770 than with the R9 280X.