What psu can power my system?

Solution
Ok, for a graphics card in that range, something around 500W would be decent. A 550W Rosewill Capstone or Seasonic "G" series would be great.
With no graphics card, I'd get one of those inexpensive Seasonic 300W 80+ bronze units; I think they're < $40.
Edit: That choice remains valid if you have or will add a graphics card that does not need external power, like a HD6450, GT610, on up to a HD7750.