power supply and motherboard wat should i do

[piloohanda]

hi well iam confused about one thing and that is : is it make any difference if i put 300 w or 400 w power supply for my pc.
for example i want use

"ASRock P4Dual-915GL Micro ATX Intel Motherboard"

or

"ASUS P4V800D-X Socket 478 VIA PT880 Ultra ATX Intel Motherboard"

wat should i do,,,,,, go for 300 w or 400 w coz i am gona put many stuff in my pc like 1 dvd, 1 writer, 3 hard drives, 4 rams 1 gig each, agp card 256 mb n so on like that

 

[b1gapl]

A 300W would suite that fine, but I would get 400W to be safe. Heres a suggestion:
http://www.newegg.com/Product/Product.asp?Item=N82E16817104953