To make it simple and less confusing, just go with what AMD wants.
I do not think it is a BAD card, but never tried BF3 on one.
I was simply trying to state that overall wattage can be misleading as many 500 watt power supplies from cheaper(or older) brands have most of the power(thats wattage and not voltage) on the 3.3 and 5 volt rails. These are not the heavy loaded rails on modern systems.
So 500 watts is not always 500 useful watts(this is why one can not just say. Hey I have 350 watts, can i run <insert card name here>, you may have 300 watts(25A) @ 12 volts or 180watts(15A) @ 12 volts). Quality should ALWAYS be the number on thing to look at in a power supply.