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.