This whole interconnect is a little confusing particularly if you want to plug multiple computers into a single monitor. The easiest way is to just have different connection. Most monitors autosense so just plugging thing in work weel. The long and short is that:

1. HDMI does support 2550x1440 at 60fps with most cables (HDMI 1.4) and you should make sure to get a 18Gbps cable to do this. These cables will even support 4K at 30 Hertz, but not at 60 Hz.
2. Some monitors have Displayport and you then need a mini Displayport to Displayport adapter which is $4.63 from Monoprice (Product Number 5714). 3. If you want DVI input, then you have to careful to get an adapter that supports dual DVI. Mini DisplayPort to DVI Adapter - Monoprice.com which is very cheap is a passive connection and only works up to 1920x1080. To make this work, you need an active component like Mini DisplayPort to Dual Link DVI whichs costs a fortune at$70.