No graphics card pulls 300W
 

Now, the highest-end graphics boards can pull a maximum of 75 Watts from the motherboard via the PCIe x16 slot, and every 6-pin PEG power connector will yield additional 75 Watts. So, in case of 8800GTX and R600XTX, we are talking about 75+75+75 = 225, or a maximum of 225 Watts. This is the maximum amount of power that will be eaten and dissipated by an Nvidia G80 and AMD R600 based product.

my 480 U15 Tgan is happy about that because it will have to handle a GPU upgrade once the x1800XT 512MB doesn't cut it anymore