To rectify being upset you can go get a nice new reliable ATX power supply and make your computer work properly and safely.The new PSU(go with Seasonic or Corsair) will also have higher efficiency and it's power output will be more stable than anything that ever came in an old Mac.

*edit, actually, SATA cards are not much a load and any normal SATA HDD is likely to either use the same amount or less power than ancient SCSI drives.