Sorry for not reading all the comments, but I wanted to make it short and sweet. I just purchased the Killawatt, and it's an awesome device (Really does seperate the BS from the truth), but here is the kicker, and this is what you need to pay very close attention to. It's not the Wattage that typically kills the system (This is in response to Sean on August 2005, replying because it needs to be out there and I don't know if it was said) It's the amount of Amps on the 12v Rail that are of significant importance... Let me give you my example... I recently purchsae a Corsair 650watt power supply. Thie 650 Watts is cute, but the important thing about this power supply (What makes it quality) is it has 52Amps on the 12v Rail. You want to account for a majority of your devices being connected on the 12v rail. With my 1090T, 5770 (Crossfire), 4Gbx2 Gigs of Ram, 3HDD, 1 DVDRW, and a Thermal Take 760i (Plus Fans) I get about 240watt... When playing World of Warcraft, I hit 270watt... If you take the Total Watt consumption, and divide it by the volts pushing it (it's on a 12 volt rail) You get a realistic representation of how well your Power supply fits in (FYI, if your powersupply doesn't at least tell you how many amps on the 12v rail.. It's not a quality Power Supply) At 240, I am approximately 20Amps.. At 270Watts, I'm at 22.5 Amps... If my 12v Rail supplys 52amps, then I'm in the clear as I'm not even approaching 30 yet. If Someone wants to correct me, feel free, I like learning as well!