bandage485 replied: "Really the best person to answer that question is yourself. Every device you put in your computer displays the amount of power it uses right on the box. Add them together and you get a good estimate of what your system uses.
Be sure not to cut the number too close though, giving a PSU breathing room goes a long way towards its longevity.
I'll help you break it down if you dont have the means to get the numbers you need.
Look up your quad core online - power use varies a lot with CPU's. We'll say 150 watts
PCI-E card - 45-75 watts
7200 rpm SATA drive - 5-20 watts
DVD drive - 15-25 watts
Case/fans - 3 watts each
Motherboard (w/o cpu/ram) 30-40watts
Ram - 10watts per 128MB
So with what you have in your system right now - thats roughly 400 watts of power used. (You yourself can get a much more exact number though)
So another couple drives, another PCIE card, and another HDD will put roughly an extra 115 watts of strain on your PSU.
Looking at what you got, i would say 650 would be plenty enough enough.
And don't forget, a computer only uses the amount of wattage it needs - buying a 1000 watt PSU wont make the computer run any stronger, but like i said earlier, don't cut it too close or that PSU wont last as long as it could have.
Goodluck"
Yggdrasil replied: "If you go SLI, get at least a PCP&C Silencer 750W or 810W. Warning, above 750W, PSUs get noisy.
...and, of course, get 'em at NewEgg."

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