Sat 10-Nov-12 03:04 AM | edited Sat 10-Nov-12 03:04 AM by ShrimpBoy
Lens questions really should go in the lens forums.
Looking at what you listed, I'd say the 18-105 and 70-300 are your theoretical weakest lenses. The latter especially could be replaced fairly cheaply (under $400 these days) with a used 70-300 VR. But what you've got isn't rubbish and with good light and good subjects should produce good images.
Before you change anything, look through your collection of images and get the statistics on what lenses and what focal lengths you tend to shoot. There's no point getting a better version of something that's never on your camera anyway.