Dont forget if you are cropping an image, especially with the D200 you will reduce the quality of the image. I think its only a 6mp camera? My boss had one he was never happy with it really, but it did produce some great shots.
This link explains why all digital images need sharpening post processing, and how to do it.
and a thread on it here:
http://forums.dpreview.com/forums/read.asp?forum=1029&message=22771016
You should maybe look to joining a photography forum too, you will get loads of help and advice there.
http://www.photoshopsupport.com/tutorials/sharpen-an-imag