What PSU should I buy?

[allen johnson]

I need help in choosing what PSU should I buy.
my pc:
cpu: phenom x4 II 955
mobo: asrock m3a770de
2 hd
GPU: HD7770

I have a corsair vs450 but I'm planning to buy a sapphire 280x gpu(i will upgrade my cpu and mobo too in the future) but I need to upgrade my psu first. How many watts do i really need? I'm not planning to crossfire or SLI my rig. does a 500-600w psu is enough?

choose here

 

[GhislainG]

The Seasonic S12II Bronze 620w and the Antec HCG 620w would be good buys.

 

[DonkeyOatie]

The Seasonic Bronze 620.