Basically what the title says. should i get two gtx 780, two r9 290x or a radeon hd 7990. To me prices don't matter since all of these are roughly the same price. I will be gaming at 1440p and will mostly use my gpu for extreme gaming, video editing and for doing high end projects.
Do you care about screen tearing and stutter? Vsync input lag? If you don't care, go with AMD and hope freesync will work other than just on laptops.
If you want smooth gameplay even when the FPS dip, then go with Nvidia and check out their gsync tech.