What Martin Said. we are now actually on the third gen FX CPU's, like Llano, Trinity and Richland, only AMD refreshed the the second to third FX silently.
I have had built several FX-8350 rigs for others in recent times, its not difficult to get them running at 4.8Ghz on a half decent air cooler, this is coming from someone who owned a P-II 1090T running at 4.1 to 4.3Ghz at best, the FX-8350 is a significantly faster and better chip.
personally my advice to anyone with a Thuban and an FX compatible motherboard is to upgrade to the FX-83## if they can get most of the money together from selling the Thuban.
Failing that an i5 is a more 'consistent' performing CPU for games, having said that i agree with what you have also said, the FX-83## is not a bad chip, at worst in something like World of Warcraft its still running something like 80 FPS, which is also significantly more than a Thuban 1100T.
£110 for the 8320 or £140 for the 8350 is the best CPU there is for that money.
I would be perfectly happy to run the latest version in my gamers rig if i didn't already have an i7.