What else is in your Dell drawing power? You may have problems finding a non-Dell power supply to fit in your case, but it's possible the 250 is enough. You should be able to find the power spec's for the cards on ATI and nVidia websites to help you compare against the 4400. I'm not sure about the X1300, but the X1600 requires an available 4-pin power plug. As long as you can return a card, just try it for a couple days.