I haven't done any advices yet, didn't I? ^^
Just wanted to let you know that if you got a 280X there is no need to upgrade for the next 1-2 year/s since you got a quite good mid range card which should handle everything on 1080p with small decreasing in gamesettings.
To sum up: jumping to a better mid range card like the 290 would be a too small performance jump for the bucks you pay for a completely new card.
Hold your money back for a while and get a fury/nano or even a new "arctic island" card if they will be available in the future in which you finally want to bump up your graphical performance.
Tahiti is an old name from an AMD-GPU (28nm architecture) since the amd 7xxx series.
It was the peak of the 7xxx since the 7870 boost.
Furthermore, cards like the 7950, 7950 boost, 7970, 7970 GHz edition and the allmighty 7990 with its' 2x Tahiti GPUs called "Malta" had this GPU in it.
The 280/X is a more or less "redesigned" version of this cards.
280s' GPU is called "Tahiti Pro2" while the 280Xs' GPU is called "Tahiti XTL".
But all in all they got Tahiti GPUs.