Really I would go with a single powerful card. Depending of course on what you're planning to play. Have a list in mind already? Really the dual thing just seems to be buggy at times and unstable for me. In all honesty unless you're running something bigger then a 24 inch and above 1680x1050, single card is almost much better suited. Power consumption is another thing to take into account. Really either could be fine, but a single card will do most people okay. Very rarely will notice any major difference from about 50 fps and up.