I wouldn't get either. Is that 300 (377 dollars) to 400 (503 dollars) for the whole build or just the CPU? I would go with a SB Pentium G or an I3 over the Bulldozer. The Bulldozer just really isn't that great of a CPU especially for gaming.
First of all the Bulldozers aren't what they claim. They are modules not real cores. So the 4100 Bulldozer is really a dual core, the 6000's are really 3 cores and the 8000's are really 4 cores. Secondly more cores doesn't mean it's better especially with games Right now most games only use 1-2 cores. Very few actually make use of three or four cores. Lastly even at a lower clock speed and dual core Pentium G or I3 will outperform the Bulldozer in games.
i5 too expensive .. but with the AMD FX-6100 you can overclock??
okay, is AMD FX-6100 fast tho?
AMD FX-6100 vs i3 which one is faster? i3?
At stock clock for clock the I3 will be faster in most games. Is the FX 6100 fast, compared to a Pentium 4 yea but compared to real compition no. The older Phenom II's like the 955 or 965 are faster. As for FX vs Intel The Sandy Bridges and Ivy Bridges wins out even at less cores and slower clock speeds.