On the other hand, think of how much gear we used to run on a similar amount of power... in 2000, I had a 300W (it was sparkle power so it was probably a true 300W) PSU running 2 P3-800s, 3 SCSI hard drives, a CD rom, on a L440GX motherboard with 4 sticks of registered ram, onboard dual SCSI controllers, networking, video and a 64bit PCI RAID controller plus 7 case fans in a 2U enclosure. I'd say I was probably using more power than what quietus is proposing. The real wildcard is the quality of the PSU- is it really putting out 275W?
ps, we also once ran 16 drives (1.6TB baby!!), 2 3ware 8port RAID controllers, CDRW, dual athlon MP1800s from a 450W PSU. That sucker is actually still in use today, 5 years later.