[WMBP]

I'm not crazy about flash photography and have been using the built-in flash on my K100D when I absolutely had to use a flash. But now I'm thinking about buying a proper flash unit. Problem is, I don't understand the options. There seem to be two different Pentax units (360 and 540), something made by Metz, a couple of different models by Sigma and another couple by Sunpak.

I have read other threads and I gather that the Pentax 540 is regarded as an excellent choice. But it's a bit more expensive than I'd like right now. I could of course just go with the Pentax 360, but I'm trying to understand the differences and options. I gather that the Pentax 360 is similar to the 540 but does not have a swivel. What about the other brands? One of the Sigmas is about $150 at bandhphoto.com, and that's about what I'd like to spend. Any reason to worry about third-party flash units? And what about Sunpak? They inexpensive, which is good. But is it the case here that you get what you pay for?

I'm open to any kind of advice here. I'm not so much looking for recommendations as for explanations of the options, so I can decide for myself with some understanding. Thanks.

Will