DVI Single Link and DVI Dual Link

Dual link and single link DVI are interchangeable. Dual link DVI uses all of the wiring on the connector, so that you can use resolutions above 1080P and use higher refresh rates on 1080P and below. It wont matter if any of your monitors are not using above 60Hz on 1080P so just use whatever cables you can find.

Sorry, dual link dvi is not dual or second monitor.
You will need to use the display port (DP). If you plan on eyefinity or stretching your desktop across all 3 displays then you need a monitor w/ DP or use an ACTIVE DP adapter. If you only want 3 seperate desktops then a passive adapter will work and eye-finity and stretching will not.

edit - I should mention that the passive DP adapter will allow you to strech across 2 screens but not the 3rd.