I am trying to get a light setup built and have two umbrella kits on their way. I am going to get an SB600 which will sync with a D90, and was wondering what another option could be for a flash (less $ than the SB600). Would the SB400 have any use here? I have read that it won't fire as commander and I don't believe it can be used in any way off camera. Could anyone recommend some options that I could look into? Thanks!