#5. "RE: Considering purchasing lighting and need advice on what to buy" In response to In response to 4
According to Photo Strobe Trigger Voltages the sync voltage for the Vivitar 2500 is between 10.95V and 14.75V which is safe. I would recommend verifying the sync voltage yourself. You will find a link to the instructions under the "The Strobist List" heading at the top of the page. Good Luck and Enjoy your Nikons!