This system'll have an E2200 CPU, 4G RAM, 8x1T SATA drives, 1x250G IDE drive, a hardware RAID card, couple of small addon fans, no optical drive or addon video. For the sake of simplicity let's assume a slight overestimation of 15W for each 1T drive and 10 for the IDE, that comes to 130W total just for the hard drives. What do you think rest of the stuff'll add up to?