no single card is overkill for 1440p at the moment. even the fastest consumer cards in the world won't give a steady 60fps in some games.
they are all way overpriced though, so i guess you could look at it that way. you really need to look at some benchmark sites and compare value for money. from what i can see, the 290x is 5-10% faster than a 290. in australia, the 290x is 34% more expensive than a 290. so the value for money difference is huge.
if you do get an amd card, make sure it has an aftermarket cooler (an open fan design with 2-3 fans. not the standard single fan with heatsink)