There are good 700 Watt PSU's and there are bad 700 Watt PSUs. Bad 700 Watt PSU's can only hold 550ish Watts. Good 700 Watt ( Good long lasting parts that won't break easily) can easily handle 1 GTX 650.
I know this because of multiple failure PSU products that are cheap.. Cheap doesn't always mean good XD.