Originally posted by Dags I like my K100 and like the pics it produces, but I hear so much from people about getting 10 or 12 meg cameras.
People who don't know better, sure. Most serious photographer know more pixels are not necessarily better. Sure, a little more resolution (but you're probably limited as much by your lenses as by the sensor). And of course, you can crop more. But you risk more noise, too, and have to deal with bigger files and slower processing times.
Quality wise, I have no experience with the Sigma 55-200. But if you're thinking about the possibility of wildlife, either a longer lens or more pixels from cropping would allow you to get more closeup shots of distant wildlife. So results would be "similar" either way - although I strongly suspect the Pentax 55-300 would also be higher quality than what you have now.
Still, if it were me, rather than either of these, I'd be looking at getting at least one lens for low light, Africa or no, because I cannot imagine photography without one. Something with a maximum aperture of f/2.8 or better. Browse these forums and you'll see no end of discussions about FA50/1.4 versus FA35/2 versus DA40/2.8 versus DA35/2.8 versus the various manual focus options (used).