Computer power supply video card problem help?

so recently i have ordered this (video card)http://www.newegg.com/Product/Product.aspx?Item=N82E16814102838



but people saying i dont need a power supply to support my video?

my current computer only has 250w and i dont think my computer can handle the video card. and i need the video card to play games. any help?|||you need at least 400 watt power supply i woul recomend a corsair power supply