XFX, Seasonic, the EVGA G2 or G3 lineup, or filter through the Tier 1 or Tier 2 list. Stay away from EVGA W1 or B1 units... A quality 450w unit will be plenty to power that system, however check prices on 550w units as they are sometimes the same price.
http://pcpartpicker.com/products/compare/fZyFf7,xVkD4D,3pqdnQ,2tckcf/
PSU Tier List => www.tomshardware.com/forum/id-2547993/psu-tier-list.html