Don't even consider any FX9xxx series processor. Unless you downclock it to a FX8xxx series level, you will need some serious aftermarket cooling, and even then there is no guarantee of stability. Have you overclocked your FX6300? Mine is stable at 4.1Ghz with a Zalman cpu cooler (and a cheap low end motherboard). With a good motherboard and aftermarket cpu cooler, you might get the FX6300 stable at 4.4GHZ or so.
But I wouldn't put any money into a 6+ year old platform, unless the additions can be transferred to a new build (cpu cooler, SSD, etc.)