Nikon Flashes

Recently I have been taking more portraits then I ever have in the past. I have known for a while that if I continued to take a lot of portraits that I should probably invest in a flash for my Nikon D5000. What I typically do is find out what I want/need and then I look at my options. When looking through the Nikon products I was presented with a few choices. The reasonable ones seem to be SB-400, SB-600, or SB-900.

I almost instantly decide against theSB-400, maybe someone can convince me otherwise, but being the cheapest Nikon product available for my camera, it is almost guaranteed to be lacking features that I will want to make use of.

TheSB-600 seems to be packed with more features, but is double the cost of the SB-400. This is not out of my price range, but I can't help but look at the next best thing.

The next best thing is theSB-900. The SB-900 appears to be the top of the line product for my camera. It has a bunch of really great features, but it cost double what the SB-600 cost. This could still be in my price range, but it's really hard for me to drop $450.

I'm leaning towards the SB-600. It seems pretty middle of the road, and as I am a beginner it will probably work well for what I need. What do you think?