"I currently have a Phenom II processor, but I assume the FX series is better? Any suggestion on the processor would be appreciated."
the FX processor is meant to be overclocked, in fact, the FX line exist for this sole purpose, so you will need a mainboard supporting this feature, also ram for that purpose and of course a psu that can provide extra volts and watts for the extra load
if you are not planning on doing that or you are more concerned about system stability, this feature won't offer you anything and you will end up not using it, so perhaps invest the money on other parts could be more beneficial i think