|The optimal resolution depends on the graphic card and the monitor.|
So if the graphic card supports only lets say 1280 x 1024, the max resulution for you is exactly 1280 x 1024.
If the graphic card supports a higher resolution, lets say 1900 x 1200, the limit is the monitors max resolution 1680 x 1050.
Also see the manual, search the web or ask your dealer for the refresh rate at a resulution of 1680 x 1050. This can normally be adjusted in the graphic card settings, to match the max refresh rate of the monitor.
There may also be an INF file available for your monitor, where all the settings are defined.
You can install the INF file for your monitor and get automatically adjusted the refresh rate on changing the resolution.
Hope that makes things clear.
Please send a reply, if you solved the problem !!!