Open the case, look at the label of the power supply. Tell us what is written there. We are concerned mainly about how many amps you have on the 12v rails. The combined figure is very important also.
AC INPUT(50-60Hz): 100-120V~/9A
DC OUTPUT: +5V =/22A, +3.3V =/17A
+5V AND +3.3V SHALL NOT EXCEED 150W
+12VA AND +12VB SHALL NOT EXCEED 264W
MAX OUTPUT POWER: 305W