whats the money situation, its a really big deal for this cause 1440p id gonn arequire one hell of a single card or two decently expensive cards. And although you will save money buying two cards, not all games are compatible in crossfire and SLI
the most beastly single card you can find will you be the best choice, as for the price and such though thats up to you. Also, if you alrdy have your gaming set up, i would wait for some of the flagship maxwell GPU's to launch even if you dotn buy one, the price of the current flagship (gk110) is gonna go down when the new silicon hits the market.