Well, understand the bulldozer was (if anything) a slight step back from the mature Deneb... the piledriver puts it a little bit ahead of the Deneb in most tasks.
generally Piledriver is about equal to a 1st gen iX series chip. The lone exception would be the fx83XX chips, which (all things being equal) are roughly at the level of an i5 when overclocked.
generally speaking the 63XX series is somewhere between an i3 and i5 in performance. When overclocked it can reach a lower level i5 in performance. the 43XX is a bit slower then the i3 unless overclocked. basically, this is the trouble the fx runs into. At the low end, while their prices make sense the FX doesn't come with an on-chip GPU, so while an fx63XX or even fx43XX would make sense over an i3, generally you only really take an i3 in situations you're planning on using the on-chip gpu anyway, or in builds that are designed for lower energy use, which of course you're not going to get from an FX chip.
The FX 63XX fits into a weird niche where someone who wants to build a gaming machine might find themselves but doesn't need the performance of an i5 or doesn't quite have the budget for one... you see my point about a weird niche, it's really ideal for people with small (non-hd) monitors with 60hz refresh rates so you'll limit the impact of the cpu on your gpu, because while it will overclock to an i5, anyone who wants to overclock it to those levels will probably want to overclock their i5 too... in short if your gaming budget is something around like 500-800, you might get a better gaming machine from the fx6300, as you could take money saved on the chip to spring for a better gpu or ssd which would likely make your gaming machine really roll over the superior cpu intel budget build.
the fx83XX is yet another inbetween chip, when overclocked it will pace the i5-i7 series in most singlethreaded tasks (though it's still slower then them, generally it is close enough overclocked to not matter much), which it's a really heavy lifter in multithreaded task in line with a high end i7. Which again sorta hurts the fx83xx chips... because gaming generally is all about single-threaded performance, as is video encoding, so in those two cases you're going to take the i5-i7 as overclocked they tend to outperform the fx83xx series decisively.
Which of course means in the end unless you want an AMD chip or are on a budget and accept it's disadvantages, the general advice is to buy an intel chip. AMD makes sense in certain price points and with certain builds or situations, and of course it's doubtful you'd notice much of a difference between an fx83xx and an i5 or i7... i mean the difference isn't THAT significant, but when measured it certainly exists.
