I do not have the funds for a SB-900 at the moment, but will be getting one in the next couple of months. I do have some funds for a SB-600 now. Would I be better off getting the SB-600 now, and using it as a slave later to give me more flexibility after I get the 900? I know I would like to have more lighting options down the road, but for now the budget only allows what the budget allows. I guess I was asking to wait and get the 900 later, and then see what options I have for adding a second strobe then, or go with the 600 now, knowing the 900 is coming?