It seems that your aren't using the new Intel driver but maybe your card isn't supported. Since xrandr shows the correct resolution you should be able to choose 1680x1050 under System - Preferences - Screen Resolution.
It seems that your aren't using the new Intel driver but maybe your card isn't supported.
Since xrandr shows the correct resolution you should be able to choose 1680x1050 under System - Preferences - Screen Resolution.