Normal
I am going to be doing a build over the next year or so with a flex atx power supply as well. The best one I found was this one. Notice that you can choose it at 400 or 500 watt with a Noctua fan. I'd love to use this one but sadly the custom work on it makes it too long (170mm) for the case I want to build. I will personally have to go with the FSP 500 gold. I've never done this and don't know how to, but you could always replace the 40mm fan in the FSP with a Noctua 40mm.