i always look at power supplies like cars when it comes to size. if you take a car and run it at full throttle all the time its not going to last very long, if you take that same car and run it at 50% throttle chances are its going to last a whole lot longer. same thing with power supplies, if your drawing from it at 100% of its capacity its not going to last very long. (also, a system is only going to pull the power it needs. if you have a 500 watt power supply, its not putting out 500 watts all the time. it just gives your system access up to 500 watts.)
first thing when looking for a power supply is you need to size it. use a power supply calculator to come up with what your theoretical power requirements will be at full load. from there i would double the amount required for longevity with a limit being at 1200 watts since the average breaker will be limited at around 15 amps. next go with a brand you trust. i myself highly recommend corsair, they come with 10 year warranty and are some of the highest rated on market. and another thing to long for is to see how many 12v rails the power supply has. they will list this in the amperage rated section in the specifications as 12v1 12v2 etc.. i recommend going only with power supplies with a single 12v rail so all your components have access to the entire pool of power. having multiple rails is more of a cheater and cheaper way of producing a high wattage power supply. with a multi rail power supply you have to balance your 12v parts across the multiple rails. if you have too many items on one rail you risk overloading that rail and your power supply will act more like a much smaller one. realistically go with a power supply with a single rail and save your self the headache. corsair power supplies are all single rail. for as much as i talk up corsair, you would think i work for them.... time to get sponsored!
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for my build i went with a 1200 watt power supply, my reasoning was for future proofing on any extra parts i may add ass well as longevity. i think the most i have pulled from it was about 620 watts and that was with everything listed below minus the fury x and add 2 HD4970's. its been 4 years so far with out a issue, and alot of that time it ran 24/7.
hope this information is helpful!