I like my 70-300 VR. The contrast is seems good to me and if I want more I could fiddle with the camera settings or later say, "Hello post-processing!"

It's just about the easiest thing to adjust. I took this yesterday with the 70-300:
https://forums.macrumors.com/threads/204316/ picture #5896
It would be nice to have a wider aperture, but price and weight sky-rocket. As it is, the 70-300 is a good compromise for amateur use.
The 18-200 range is great, but the price
is steep considering the reputed medium quality of the output. (I'm just going by the reviews, of course.)
I'd say keep the kit lens and get the 70-300 because that extra 100mm reach does make a big difference--much better bokeh, tighter framing, etc.
If weight/size is a concern, however, then choose the 55-200mm. It looks sweet.
If you really hate to change lenses or you are always traveling, then get 18-200mm.
If you're worried about the price differences, maybe waiting until you can afford what you really want might be a good idea.
Also, keep in mind that the equipment is only part of the quality-photo equation.