Yeah, what they said. I have a Nikon D-80 setup and the quality flash is around $150. For the same price I can get a 50mm f/1.4 which is far more valuable, considering the effective range of most flashes.
If you're shooting wilderness stuff, I would encourage prime lenses (fixed focal lengths, i.e. 400mm, not 80-200mm zoom) and a quality monopod.
There's data about hand shake and its impact at certain focal lengths, but I'm too lazy to look it up.