Flat panel ? I assume it's a TFT. Well in this case you should run it at its native resolution (for 17" it's usually 1280x1024), then it will give you the sharpest and clearest picture.
Also run it at 60Hz, it's the best for TFT's.
17" TFT. . cool, I envy you, only have 15" TFT
RJ