I have just bought a 2560 x 1440 monitor for my macbook pro. I've tried the mini DisplayPort to DVI and the mini DisplayPort to HDMI cables to connect to the display but both will only push 1080p to the monitor. Will a mini DisplayPort to DisplayPort cable run the resolution or do I need the dual link DVI adapter?
Mini Displayport to Displayport is the best solution, provided your monitor has a Displayport input. A mini Displayport to Dual-link DVI adapter is also a possibility, but those tend to be expensive and not always reliable. If Displayport is an option, go with that.
I had issues trying to use a HP Z30i with 2560 x 1600 resolution. The only way to drive it at full resolution was with Apple's Mini DisplayPort to Dual-Link DVI Adapter
Other approaches (HDMI, Mini DisplayPort to DisplayPort, and Mini DisplayPort to DVI) only provided lower resolution (1920 x 1200).