How deals Surface Pro 3 with HD monitors?
Solution 1:
Surface Pro 3 can drive up to three external displays. As you asking about just single, here is excerpt of my own edit on the Wikipedia, slightly rephrased:
In a single external display mode over DisplayPort, the i5 and i7-based models support resolutions up to 3840×2160 at 60 Hz, known as 4K Ultra HD.
So yes, it's possible to connect your 2560×1440@60 Hz Dell display to your Surface Pro 3 via Mini DisplayPort. You'll need either Mini DisplayPort — DisplayPort or Mini DisplayPort — DVI-D DL cable or suitable active adapter.