1920 x 1080p is standard. So is 2560 x 1440p.
R9 280x is a good solution because there is 3gb vram and more processing power than a 290X which has 4gb vram. But it uses more power than a 290x. And costs more.
R9 290/x leaves an upgrade path (290/x xfire). But 3 way xfire is hard to get motherboard, lots of power and bad scaling.