I want to buy a phenom II x6 1090t be cpu, a mobo that supports it like a 780g chipset, and 4 gb ram (1333 MHz). I only plan to use on middle range video card. Would 400 watts be enough to cover all of that? What other info. would you need? Do all of the psu's in the last couple of years have the same connectors so that any one would fit on my mobo?
A 400w unit from Corsair, Seasonic, Antec or PC Power and Cooling is enough to run that system with up to a HD5770 or GTS450. Probably a GTX460 would be fine but you are cutting it close. If you want upgradeability then a 550w unit from those manufacturers will run just about any single video card on the market.