I'd say that you should get the 6300. The Athlon will not be good, considering that it is a bit outdated. I wouldn't go for that unless i'm on a budget
Looking at your build I see that you have a high priced case and more RAM then is actually needed. I would go ahead and get 4gbs RAM and like a $30 - $40 case and put the extra money toward a better card. a R9 270x is a better purchase for the money you'd save if you take my advice with the case and the RAM. You could also get an OS for free if you want 😉 that's totes what i'd do.
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