I have just invested in a Sony Alpha A200 SLR, and am wondering about lenses. I have heard from the pros that 'the lens is more important than the camera' etc. The camera came with an 18-70 kit lens, that I'm finding to be great (my last camera was a cheap P&S, so anything would impress me I think). I have heard disparaging things, however, about kit lenses in general, and am thinking about getting a better zoom lens, something like an 18-200. It is worth it (apart from the obvious extra zoom power)? What kind of difference in image quality will be obvious?