What is trace lenght? What trace size are you using ? Is it poin to point?? How many layers?
There is no straight answer for your question, check Howard Johnos book Black Magic, or look for the Eric Bogatin books. Alos Xilinx app notes will help
In Virtex -2 datasheet it provides few impedance control methods.
What I am confusing is do I need extra impedance control if I have used one of those impedance control methods provided by virtex-2 datasheet?
again no straight answer you might you might not. Also check the Xilinx for the development board, try to order one of those boards, and see how they behave. or simple run quick protoboard