If you do two 660s, you're going to need a better PSU. Also, I would suggest a Corsair or a Seasonic PSU for this build. Also, i'm not sure about that motherboard but most only support up to 1600 or 1333 mhz RAM, unless if this one supports 2133 Mhz there's no point in getting high end ram. And even if it did there's not much a difference between 1600 mhz and 2133 Mhz for gaming.
if you are planning to sli you should consider getting 600w psu minmum. CX 600w is a good psu for the money.
for the ram he is right, max ram for this cpu 1866, and the extra you pay on the 2133 is a rip off. 1600 is enough.
this almost like my build but i have the fx 6300 instead of you cpu.