i.e.
A: It's delicious! You are so good at cooking!
B: ___________. (Something like "No, that's not true. It's just my mom is good at teaching me how to cook")
Well... I went to Asus Site and it recommended 600 W for what you wrote here... :S
Maybe you can try google for "power consumption calculator". There will be a lot of tools that helps.
Good idea.
Most important thing is your graphic cards. The other parts really are just taking not more than 300 W.
CPU: 100 W+/-
HDD: 10 W+/- per hard disk
MoBo: Usually not more than 50 W (I don't know)
Graphic card: ???