by c_hegge » September 10th, 2011, 9:30 pm
There is no 80%. It's simply Voltage x Amperage = Wattage
As shovenose said, old CPU heat sinks would be great.
You could also use PSU heat sinks, but don't attach more than 1 resistor per heat sink (and if possible, use 2 heat sinks, one on each side).