How many watts necary for extreem gaming computer?

I am considering building my own computer using amd's new phenom processor (Also would it be better for me to use amd's 6400 duel core processor since most of the kinks have been worked out of it. And since the new phenom cant be overclocked functionally to more than 2.6 ghz?) Back to the real question. Watt is the average wattage of a computer with this kind of setup. I will also be using a liquid cooling system, a minimum 22" lcd monitor, ino 3d 8800 gt (factory overclocked) grahpics card, corsair dominator memory, two wd 160gb harddrives, oh and I may get blueray disk drive later, plus minor add on. Hope you guys can help me out with this.