It really isn't worth it. At least not for Planetside 2. That game is really only optimized for one or two threads. The Phenom IIs have better per core performance than the FX series. Especially the 8120. I'd just try and keep pushing the Phenom or grab an Intel.
You will want to upgrade your GPU soon though too. I would wait until the R9 3XX cards drop tho
I have an FX-8150, and it runs more smoothly for a lot of stuff compared to the Phenom. I mostly use MS Excel, Access, SQL Server and occasionally other products (SPSS, Visual Studio, MapInfo,...). I think it is a significant improvement. There are deals now where you can get an 8320 for $100. I think it is worth it. Also, if you go six-core, go 6350. It is far better than the 6300.
Also, I upgraded from a 6950 to a 660ti a few years ago, and WOW, what an increase. you can get those on ebay for super cheap right now, and the performance can get within a hair of a GTX760.
All the programs you listed for the most part can take advantage of multithreading which the FX series dominates. Planetside 2 isn't one of those programs though.
Opps, I did mean the FX 8320. Is it safe to safe that changing GPU's would bring me a FPS boost to planetside 2?
I did think about changing to intel, but I want to hold on and see the next desktop orientated CPU (non-APU) coming out from AMD that supports DDR4. Any guesses to when it will come out?