The Thermaltake Power Express 250W is a video card power supply specifically designed for the needs of current high-end video cards. When you have an older PSU you may not be able to run Crossfire or SLI because the PSU can not supply enough power for the video cards to run stable. When installed, the Power Express will supply 12V to your video card(s), taking a lot of strain off your main power supply.



Link: TechPowerup