On LCD monitors you really should use the native resolution. That represents the actual number of pixels that make up the screen. All of other resolutions will be imperfectly displayed because of pixel distortion to fit the new resolution on a improper number of display elements. The native resolution should not look "squished." If it does it is more likely an issue with your settings than the monitor. Try changing things, gpu scaling in particular might be set wrong.
1440x900 isn't significantly higher than 1280x960, it is just a different aspect ratio, so the advice about the card remains the same.