It is possible to change the PSU and add a powerful graphics card, but it is important to check that the new PSU is compatible with the system and can handle the power required by the graphics card. The current power supply is a 600 watt Power Boost 80+ Gold, which may be sufficient for some graphics cards, but this will depend on the exact specifications of the card you wish to install. It is advisable to consult the technical specifications of the graphics card you want to add to ensure that it is compatible with the existing system.