I want a flash, most likely either the SB600 or SB800. But I'm no pro and have very little experience with flashes. What's the main difference between them? How does the wireless feature work on the SB800? Does it need a IR trigger on the camera, or any other equipment? I'd mainly be using it as a fill, at a variety of lengths, if at all possible with the flash mounted off the camera. This makes the 'wireless' feature sound appealing, but largely the SB800 seems the same as the SB600. I use a D80, btw. Just looking for experience and advice, on either the two mentioned flashes, or something similar?