If the PC's gonna be used for gaming, then I recommend the FX-62 definitely. But otherwise, the 5000+ is the best one IMO. However, why are u going with such expensive AMD processors, when an Intel Core 2 Duo E6700 can easily beat all of them for much cheaper?
What exactly do u mean by the above statement?
Anyways, Core 2 Duo is the way to go for any new PC right now. But if you want a future-proof AMD solution, then Socket AM2 is right for you, since the K8-L processor line will come out soon and is expected to match/blow away the Core 2 Duo's performance. For now though, Intel is king.