Antec Neo HE 550 Power Supply
 

To own an enthusiast level system today means you have in your midst a Power Hungry Monster! Why do is say this? Well here's a perfect example of my rationale: A few days ago the best Extreme PSU Calculator that I have found to date over at Outervision eXtreme. This calculator takes everything and I do mean everything into consideration I ran my current system through it and determined that @ 100% PSU utilization I needed around a 500 Watt PSU. I then wondered at 100% utilization how much of a lifespan would my PSU have? Not to mention cooling. I have always been told that a good rule of thumb is even in those full load, overclocking sessions where you're testing the maximum your system will deliver you should not stress your PSU more than 90% for a prolonged period of time. I personally prefer to drop that percentage down to about 75% for periods greater than about 10 minutes and 90% to 100% for short term testing of less than 5 minutes in duration.