The FX-4100 would be an improvement, but the FX-41xx, 61xx and 81xx are notoriously bad CPUs. AMD's Bulldozer architecture performed very badly when compared with Intel's processors at the time, and were even a bit slower than their previous CPUs that they replaced, the Phenom II's.
I would suggest either a Phenom II x4 or an FX-4300, depending on what price you can get.