i have a somewhat old hp pavilion with an amd Athlon x2 and a 300 watt power supply. i picked up an ati r5 230 gpu from best buy for the hdmi port to make it better suited for a movie server/htpc. now the box recommends a 500 watt psu, but another source states that it only draws 27 watts, but also recommends a 500 watt psu. i already ordered a cheap 500w psu, but can i run it on the stock 300w?