I'm trying to connect rMBP to a 30 inch monitor (Dell U3011t). The native resolution of the monitor is 2560x1600. (1) I first tried to hook up with DVI cable. Failed. It says that I need a dual-link cable, which is expensive. (2) HDMI cable works, but can't get to the maximum resolution. I can only get 1900x1200 resolution. What should I do? Do I must buy a dual-link DVI cable? I'm so confused.