if you want cpu under $100 then simply get intel g860.
intel g860 beats fx 4100, fx 6100, fx 8120
see here- http://www.tomshardware.com/reviews/gaming-cpu-review-overclock,3106-2.html
Its better GAMING cpu at stock, but its not faster overall and its not a better choice either. The 4100 can overclock fairly easily while the G860 cant. In fact, the 4100's big brother, the 4170, in that same article tied for best gaming cpu between $100-$200. Take a look:http://www.tomshardware.com/reviews/gaming-cpu-review-overclock,3106-3.html
The only difference between the 4100 and the 4170 is the multiplier setting. Which is unlocked in the 4100. Buy the 4100, up the multiplier to 21, and you have a 4170 for half the price.
At $79, thats tough to turn down.