well 18mm is 18mm so you will get as wide of a angle with that lens as you get with your 18-55 but you will get a good deal more zoom since it goes up to 200mm, that is a pretty nice lens over all, allot of people love it and allot of people do not. i seem to think mine is pretty good. its very convenient to only have to carry the one lens around.
with the 55-200mm lens you will start out at the 55mm so when your kit lens is at 55mm that is as wide of a angle as you are going to get with that 55-200mm lens.
with the 18-200 you will get a much wider angle compared to the 55-200 and a more convenient package.
if you plan to shoot wild life a 200mm zoom is not very much, for wild life a 300mm is the minimum recommendations, a 400mm is really the least amount of zoom i would want, even my 600mm lens leave me wishing i had more when shooting small birds or even big ones that are far away..
i use my 18-200mm for every day shooting and my 150-600mm lens for shooting birds and those are what i use for most of my shooting and 200mm is plenty of zoom for almost anything except for shooting small objects that you are not close too...
the 70-300mm vr lens is definitely a good lens if you want better image quality and a bit more reach but you start out at 70mm instead of 18mm or 55mm so you do not have a really wide angle with that lens. but if you have that and your kit lens that would be ideal if you do not mind having 2 lenses.
here are a few shots with my 18-200 i am not really sure why some people think its a bad lens but there are better lenses out there..
