Currently I use a 18-55mm and 55-200mm lens with a Sony A58. However I often find myself switching between the two. So I started to look for 18-200 (or similar) zooms lenses. The problem is I am only willing to spend about $250 on one. I have narrowed it down to two. The Tamron 18-200 and Sigma 18-200. Does anyone have any suggestions or tips? Thanks!