How much powerful PSU i need for my system?

[ATIFanboy]

I dont want to buy to powerfull PSU if i dont need one so how much powerfull (W) PSU i need for:

Asus P4G8X Deluxe.
P4 2.4b GHz. (Thinking to buy 3.06 GHz)
ATI Radeon 9800 XT.
2 HDD (7200 RPM, 5400 RPM).
2 System Fans.
1 CPU Fan.

Also my PC is up 24/7.

P.S. i dont asking for brand name or something just power e.g. "420 W".

 

[Blain]

- Here's a handy PS calculator -

You really need to list anything in your PC that uses PS power.

 

[ATIFanboy]

Great tool, but is it correct?

I count 450W of final output. Btw ATI Radeon 9800 XT require power connector to how much power can it eat?

 

[ATIFanboy]

Also i find this article very useful.