I've just bought a Nikon D40 including a 18-55mm lense. However, this lense does for some occasions obviously not have enough zoom. I've thought about different lenses, but since you have more experience in buying lenses I thought I'd drop this one before you. Which is a good 55-200mm lense suitable for a D40? Am I alright to get me a pretty much plastic fabricated lense, or should I go for more metalish ones?