Dig,
I believe you made a mistake, the voltage should be around 60 volts. The wattage requirement per drive may approach 300 watts.
The power supply requirement is 2/3 the total wattage of the combined total of all drives. IE (3) three drives x 300 watts = 900 watts ÷ 3 x 2 =600 watts
Welcome to the Zone,
Jeff...