The total rated wattage of any PS can be mis-leading. The +12, +3.3 and +5v are the voltages that make up most of the total rating. Alot of Ps's don't give a seperate maximum for the +5 and +3.3 combined, its less that the max of the the individuals. AMD was recommending that the +3.3 and +5 have a limit TOGETHER of 145watts, that upto about 185watts for the bigger BIRDS. Many supplies provide 12amps (144watts) or more on the +12v line, which buys you NOTHING, unless you run lots of case fans or peltier cooling. Most systems can get by with 6amps on the +12v. Thats not all, how well is the voltage regulated and what percentage of ripple affect the PS also. Some PS's don't provide stable voltages fast enough if you have a mig mutha Video Card, result is no post.