At $140, there really is NO competition.
The FX-6300 is THE only chip to buy at that price range. Simply an outstanding chip You can't go wrong with it
Edit - You can always convert your 6 core to the FX-4300, by disabling one module (2cores) and clocking the remaining ones upto 4GHz. However, there is no need to do this, as the FX-6300 in its default state is more than capable enough.
Also, nowadays games are slowly starting to use more cores, and you don't wanna be stuck with a weak quad down the road. Look at the Crysis3 benchies for example, the game loves more cores, part of the reason why the hyperthreaded dual cored i3's perform like a fart in that game.
The FX-6300 is also a very good multi-tasker, and in workloads that can use all 6 cores, it comes very very close to i5 levels of performance. Examples are video conversion, photo editing, winrar compression etc