I'd rather have the "slower" dual core over the fastest single core avail, for slightly less money spent, for it's multitasking...
As Nvidia/ATI drivers and various games (Quake4, so far, as COD2 SMP patch sux) are already becoming more optimized for dual cores, an most high res gaming is gpu limited anyway, the extra core is very nice.
Example: A $220 3500+ scores only 1 or 2 fps less in FEAR than a $1000 FX57 at 1024x768/4xAA/16xAF...
But look at Quake 4 once SMP patched....a $280 Pentium 820D spanks a $1000 FX57....