you should use around 15-25mm on landscapes with that 1.6crop factor, so you need different lens for wildlife and landscapes, if you like to shoot some small wildlife animals from a distance you might need 1.4x or 2x teleconverter with the 70-200mm like this http://www.the-digital-picture.com/reviews/Canon-Extender-EF-2x-II-Teleconverter-Review.aspx , you can allso use it on 50mm to take macros, 2x would make the 50mm a 100mm, but still get same closest focal lenght. They are bit pricey, but still cheaper than totally new lenses or a 100mm macro lens and some 400mm lens. I suggest you shoot landscapes with the kit lens and get 70-200L if you really want a telezoom badly, if you dont need telezoom much then just get the 55-250.