the 8350 is just clocked higher out the box compared to the 8320. if you put the same coolers on them, like a 212 evo, they will both top out at the same overclock. though if your trying to reach for 5.0ghz, the 8350 may have a slight advantage since it is binned slighly higher.
the 5800k and the 7850k are so close in performance that the price difference of around $60 is just not worth it.
otherwise, like i said, the amd am3 platform is old an dying. if you need a cheap cpu for highly threaded non gaming tasks like encoding, the amd fx 8 core is definitely a good buy on a steep budget. for gaming, just get an intel i5.
at this point though, i would say waiting for skylake or amd's successor to the fx line if your tyring to get powerful cpu option. you can just drop in a 5800k now and ride out your gtx660 for the next 18-24 months and then do an entirely new build then when we will have all the new goodies. ddr4 will be the norm... 500gb/1tb ssd's will be cheap, amd/intel tock generation cpus, and near 4k capable single gpus.