Building a gaming PC

[Undertoad]

This thread is called Building a gaming PC. The HP/Dell engineered machines are absolutely meaningless on this thread.

The overall wattage number is just the added total of wattages on all rails. On gaming rigs the +12V rail is the most important, but power supply wattage doesn't break that down, so a higher wattage supply may still not provide enough power on that rail. Power supplies of 8 years ago aren't enough to run modern video cards. They draw huge amperage!

Power supplies are less efficient at 100%, do you care?

Now about upgrades. Going to overclock? Many gamers do! But never the HP/Dell engineered systems.

Going to RAID? Many gamers do! But never the HP/Dell engineered systems.

Going to have 8 sticks of memory? Many gamers do! But never the HP/Dell engineered systems.

Add memory, overclock, add a second high-end GPU and run in tandem with CLI, now you need twice the wattage on that +12V line and the 650W won't handle it.

Not only that but! As power supplies are used, they lose capacity due to electrolytic capacitor aging. What was an appropriate supply this year will likely have 20% less capacity next year.

Finally, the power supply companies lie about their numbers.

Hell, go with the 750W. You're not going to draw more wall power; actually probably less, as the unit will run more efficiently. And it may even be able to power next year's model GPUs.