I dont believe so; because the 400 watt Fortron units (although they are a great compnay) are not the same units as the high class 85% efficient units. Therfore your unit will not really put out 400 watts on an extended duration. The real output of your unit will be more like 300 watts by the time you address the heat de-ratign curve, capacitor aging etc.
another thing to consider, the unit you have most likely is dual rail ?? with PCI express connectors for video card which you wont be using for while.
the amps on each 12volt rail are dedicated to those rails, example = if you have 19amps available on the 12volt rail for your video card and only 10 amps get used by other devices, there are 9amps or 90watts of power that wont be used, as its dedicated to a "leg" which is not in full use. its doesnt get redistrubuted.
that is one of the major reasons why a unit can come up short even though it seems like it should be plenty.