psu help? with these system specs..

[jedi_jay]

hi guys building my first pc spec below def nothing great but on got a intel core2 e6300 at the mo so hopefully it will be better?

amd Athlon II x2 250 or AMD Phenom II X2 545
512MB Sapphire HD 4550 , PCI-E 2.0 (x16), 1800MHz GDDR3, GPU 600MHz, 80 Cores, DVI/ D-Sub/HDMI -
500gb sata hard drive
sata dvd writer
4gb 800hz ddr2 ram
asrock n68s motherboard

will this psu be enough watts?
350W Silverstone ST35F Silent PSU 120mm Fan Dual +12V, PCI-E, SATA, 80%+ Eff' - Scan.co.uk

or should i go with one of these?
ST40F - 400W SilverStone Strider aPFC PSU (Titanium black colour), Temp Controlled Fan (22 dBA min) - Scan.co.uk
500W Silverstone Strider ST50F Silent 120mm Fan Dual +12V, 80%+ Eff' - Scan.co.uk

i don't want to get one to powerfull if not needed also heard sliverstone is a good make have i been told right?
or is psu better? http://www.scan.co.uk/product.aspx?ProductId=19039