So I think I'm going to pull the trigger on a new flash. But I"m having trouble decideing between a second SB-600 or a SB-900. With my current setup, I've got a SB-800, and a SB 600. Usually when I'm doing multi-lighting set-ups, I leave one flash on camera dialed down a bit for fill, and a second flash at a 45 degree angle (or whatever looks best) at full power for my main light source.
I've just gotten started with this look, and quite like it, but I find I'm getting some pretty harsh shadows if I have a backdrop close to my subject. I'm thinking putting a third light behind the subject might help balance things out just a bit.
I could, of course, just use the pop-up for fill, and put the SB-800 somewhere else, but that limits me to the D80\D90, and I really like using my D40 because 1. I don't have to ask permission from the mrs. to use it, and 2. It will sync up to 1/500th of a second, which gives me more control over the ambient light.
I suspect an additional SB-600 is all I need for the above, but I was wondering if any of you 900 owners think it would be worth the extra money (another $250) for the additional brightness and gadgetry offered by the 900.