System Usage from Most to Least Important: Gaming, browsing internet, music
Are you buying a monitor: If enough money is left
Do you need to buy OS: Yes, not sure about Win8 or Win7
Preferred Website(s) for Parts: newegg, or amazon
Location: North Carolina
Parts Preferences: for CPU's, I've been looking at the AMD FX-6100 and 6300, because of the budget. If there is a CPU that I can get for better price, then please recommend. I like 4 or more cores, due to future gaming.
SLI or Crossfire: No
Additional Comments: a window would be nice on the case, I don't need it but it'd be nice. Also, a case with good cable management. Number one thing is a quiet PC
Why Are You Upgrading: because my current pc is terrible
That is a really hard budget to swing with a OS, and a fx-6300, since you need a OS included in the budget. Would you may want to consider a apu build, since really even at your high end price range, its more or less a 400 dollars hardware budget.
It's a bad idea getting that psu in the combo for a 7870, that psu is junk, a 585W psu with just 15A on the +12v rail, it means it only has 180W, the cpu and the gpu at load will surpass that, it probably will shutdown or since it's a really cheap psu, take the other parts with it.
Overall the i3 is better, both are at the same price, but you need a better motherboard for the fx-6100, those low end am3+ got low power phases and low quality mosfets, which will be more expensive than the b75 board.
The i3 is a good choice for budget gaming.