If you use a PSU calculator like the one linked above me your system will draw about 520 Watts. You always want a little headroom, or else your PSU will not run efficiently, and will not last as long.
I checked my PSU again, and I have a 580, not a 500.
there is no way that system draws 520w during gaming, I have the exact same one and will hardly break 300w.
any solid PSU with 40a on its 12v rail will be sufficient for him. of the three he linked, I would go with the silverstone, at least its rated for 34a @ 40c and 80+http://www.techradar.com/reviews/pc-mac/pc-components/cases-cooling/power-supplies/silverstone-strider-essential-st50f-es-717134/review