A good quality video-card is just as essential as a good monitor when trying edit photographic images. Look at the colour depth (the maximum number of colours available) at each screen resolution, and the refresh rates.
The more memory on the card allows you to have more colours at higher resolutions. You will want the maximum number of colours available to accurately display the colours in your picture before printing. However, remember that the refresh rate decreases at higher resolutions and you will probably want at least a 75Hz horizontal refresh rate to reduce flicker. The higher the better.
WARNING:- Do not drive the monitor at a higher rate than specified for the appropriate screen resolution or you will likely destroy the monitor, or even make it catch fire! When spending many hours staring at the monitor it is essential the picture is stable and the images are sharp without ghosting.
Nearly all modern video-cards fit in the AGP slot on the motherboard and many provide an option to change screen resolutions on the fly, without rebooting the computer. This can be very useful as you can choose the best size for the application you are using. In addition you may get the option to change the balance of the RGB settings (Red, Green, Blue). This can get you out of trouble with colour matching if you do not have this facility available from the monitor controls.
Except for one occasion when I foolishly used a Diamond Stealth video-card (which gave me no end of problems), I have used a Matrox video-card for many years and every one has been excellent. My current model is an ATI Rage 128 with 32Mb of memory, as I could not obtain a Matrox G400 MAX for my new motherboard.
When editing photos the redraw speed of modern graphics cards (when using the scroll bars) is so smooth and the zoom is instant. It is best to choose a card with the maximum amount of memory you can afford.