a quality 550W is enough for single gpu setup. You can push up to 650 if you want. 750 or higher is for two graphic cards - SLI or Crossfire depending on what gpu you are using.
Good brands: Antec, Corsair(not VS,CS,CX series), Seasonic or XFX.
If you on a budget the XFX 550 is a good choice:http://pcpartpicker.com/part/xfx-power-supply-p1550sxxb9