You never know why this CPU was binned as an x2. It could be that there is 1-2 defective cores, it could be that it wasn't 100% stable when clocked at 3.3GHz (or could meet it with default voltage). If you are lucky, it could also be that AMD produced too many X4, but needed more X2 so they just "disabled" 2 cores. Same thing would apply for OC, you cannot assume that all CPUs of a given model will OC the same, some might actually be very limited.
My suggestion is therefore to buy what you need
, the extra will be bonus.
There is a saying: if you can't afford to loose, you can't afford to win
I prefer the demotivator version:http://lib.store.yahoo.net/lib/demotivators/overconfidencedemotivationalposter.jpg
However, it doesn't really apply to this situation