Quote Originally Posted by kujoe2002 View Post
I am a firm believer that the minimum one wants to go is 550W. I prefer my PSU to be 600-800 (I have a 750W in this machine). 450W seems like you are asking alot. If you were using onboard graphics, I'd say OK.
I would argue that's no longer the case. Even for momentary draw, unless you are running a graphics card that needs dual 6-pin power connectors or more, you won't have any issues with something in the 400w range.

I built a friends systems out of this case. With it's built-in 380w PSU, it happily runs an i5-2500, 8GB of RAM, a hdd and an SSD, and an HD6850 graphics card. Under full load (prime95 multithreaded + furmark) the system draws less than 180w of power at the wall. That leaves over 50% of the max wattage as headroom for instantaneous load.