Vortez.co.uk posted a review on the Cooler Master GX 550W Power Supply

Cooler Master announced the GX series at the end of January and was showcasing these products to the world at CeBIT just last week. The GX series stand for Gamer Xtreme and comes in three power ratings - 550W, 650W and 750W hoping to target mid-range to high-end gaming systems by offering a single +12V rail designed to provide sufficient power to dual graphics card systems such as CrossFireX and SLi. The 750W version even comes with four PCIe connectors.

Cooler Master GX 550W Power Supply Review