i have the same question but mine is 450w sentey(don't know if you've heard of it) this will be my rig
athlon 2 x2 250
hdd 250gb @7200rpm samsung sata 2
ati radeon hd5770
ps: I used to run with the same psu a geforce 9600gt xfx, when i run 2d was ok, but when I started a 3d app or any game including, I felt this buzzy noise like a whistle of high frequency, anyway I sold it out and the guy told me the same on his machine, so he went for a powercooler 500w psu and stop hearing the buzzy noise.
Looks like 400w will be just about enough. My reasons for wanting to go with the the 400w PSU was that it came already inside the case and it was alot cheaper than buying a barebone and a PSU seperate. A seperate 500w PSU is only a little bit extra money wise So I think I might order an extra PSU for the few quid extra and change it over when the system arrives just to be on the safe side.
I know how to put a Computer together.. but that's not very hard so chances are I wouldn't be able to do it haha. I was just curious really since I have a couple of old computers and therefor old PSUs laying around so if it were simply just a matter of connecting two together in some way I could double my power for free. I'll just buy a PSU with more power and switch it for the one that comes with the case though since that seems like the best option. Thanks guys
Ref: parallel two PSUs. Can, But Not recommended. You SHOULD NOT connect the +12 V of PSU1 so that it is connected to +12V of PSU #2. Must verify that where you supply +12 V from PS1 is isolated from +12V from PS2.
You can parallel say 2 +9 Volt batteries as one will charge the other until their output is equal. Power supplies will never balance out and one will always be a source to the 2nd.