6300, if you can afford 8320 and your mobo supports it then 8320.
fx 6100 and 8100 and and anything from AMD with the code name -100 or -150 anything that has that one as its second digit uses Bulldozer architecture, I love AMD but we should accpet those CPUs were a flop, those CPUs which have -300 -320 -350 enjoy Pile driver architecture, which is far better than Bulldozer architecture. So no wonder fx 6300 beats 8100 easily, also look here
http://cpuboss.com/cpus/AMD-FX-8100-vs-AMD-FX-6300
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