Yes you do. They recommend a 450W PSU for a PC with that card inside. To be clear the PSU needs to be from a reputable manufacturer. There are pieces of junk out there that if something goes wrong the PSU passes the buck to the rest of the components. That means is the PSU shorts or some other catastophic failure happens it passes that dirty power to the rest of the PC and the user is very unhappy. A quality PSU on the other hand has safety features which avoid that domino effect. It also has features that deal with low power, some power surges and more than a few others. There's a world of difference between cheap and inexpensive.