If monitor has a display port connection, you can connect directly to display port. (I have tried this one as my monitor has a display port connection and it works without adapter).
If your monitor however does not have, you can try connecting cables to the DVI dual link, HDMI and SIngle Link DVI. However Single link DVI has a max resolution only. Try this first.
If not, buy an Active Display port to DVI. YOu can read more here
edit: I dont have 3 monitors so I am not really expert. I am just sharing what I have read.Edited by nightfox - 8/7/13 at 3:00pm