For overclocking and AMD you would be looking at any of the FX range and a solid motherboard - Don't bother with an APU for overclocking.
That said, if your budget could afford an Intel i5 or i7 then there is no reason other than the "I want to try AMD" to use an AMD chip, their current generations perform fairly poorly when compared to Intel's offerings, use a lot more power and produce a lot more heat which also makes overclocking more difficult.