If you're overclocking then I'd suggest an Opteron 165/170. These have the same specs as the X2 4800 and the FX60, but are a lot cheaper and likely to overclock in the 2.7-2.8Ghz range. The Opteroms just have a lower clock speed at stock and hence lower cpu multipliers (9 & 10 respectively).
If you really have the money for the FX60 then it's a great CPU. Overclocks have been seen upto around 3 Ghz. Up to you whether you consider the extra outlay justifies the potential couple of hundered extra Mhz.
The Opterons have exactly the same specs and socket as the X2s so any mobo that you were going to buy previously. The DFI nF4 range is good, for serious overclocking, the Asus and MSI range are also good.
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