2560x1440 @ 144 Hz will only work out of the box with DisplayPort. I don't know why they're saying you need a dual-link DVI cable. 2560x1440 @ 120+ Hz is not going to work out of the box with DVI because of the 330 MHz pixel clock limit.
2560x1440 @ 120 Hz might be possible with a custom resolution if the monitor will accept it over DVI. I don't know if your video card can handle 2560x1440 @ 144 Hz with DVI, but it might be possible by reducing the timing parameters.
Hey ToastyX, just wanted to say I figured this out a while ago and wanted to report back with a new thread to show others how to max out their DVI connection if that's all their graphics cards support like mine does. Your post on another website cleared this up, and I referred to it on my main thread. Thanks for the information, it helps.