would like a better quality lens to replace my 18-200mm Nikkor 3:5 - 5.6 GED, I also have a 70-300mm

Impossible.

There is no "better quality" *replacement*, i.e. you won't find any better 11x zoom!

In order to cover 27 to 300 mm equivalent focal length and get better IQ you will need at least 2 lenses, and for *substantially better* performance you will probably need more.

At this point, a few questions should be answered before any meaningful suggestion can be given:

- Where and when are you feeling your 18-200 "inadequate quality"?

- Low light capability is important for your use of the camera?

- How much weight  can you tolerate hanging from your neck or shoulder?

- How much money can you tolerate to drain from your wallet?

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Rapick
Albums: http://rapick.jalbum.net/