There is nothing wrong with a FX 8120, it is very versitile in that real world apps it is extremely fast in, while games are hit and miss there is a reason for that, most games are tailored towards Intel and Nvidia but that doesn't mean you won't get good performance.
If you are looking to fit a budget rather stick with a HD 7870 and a FX 8120 you should get solid peformance. Ultimately it is your choice but I know that many seem to think a Bulldozer just is a complete hopeless chip, which is so far from the truth.