I am considering either the 1024MB nVidia GeForce GT220 OR the ATI Radeon HD 5670 1GB GDDR5 on a new Dell and want to be able to run dual monitors. It is difficult to get a straight answer from Dell.
If the connectors are different, it is really hard to say. I've had several video cards with two different connectors and only 1 works at a time. Both the nVidia GeForce GT220 and ATI Radeon HD 5670 say they supports multiple monitors.
According to those they both support multiple, but to be safe, if the Dell site isn't telling you, you should call up Dell to make sure before purchasing. (Since these cards are produced by many manufactures who don't always follow the specifications exactly).