I currently own a Nikon d40 with the 18-55mm & 55-200mm lenses. I love this little camera, but I am upgrading to the d90 with the 18-105mm lens. I just want to know if this is a huge upgrade in image quality, low light capabilities. Am I going to notice a big difference in these two cameras? Price wise its a big difference i know that. thanks for any help/advise!