Well the 18-55mm is not really a great lens as you already know. What are the apertures for the 55-200 and the 18-135 - what you ideally want is a lens with a constant aperture so that the lens doesn't darken as you zoom in, something in the 2.4 area would be great but again, expensive. Look into renting
Steve Crow
Crow Digital Media
http://www.CrowDigitalMedia.com