Well.. Tom's Hardware asked that same question. Here is a link to their writeup.
As you can see, the dual processor doesn't offer any significant advantages and they mention that the ONLY game that supports dual processor operation is Quake. Everything else will run at really close (if not slower) on a dual system, and may be unstable because the hardware isn't supported by the game.
All in all, unless you are looking for serious prestige among your peers in the computer geek arena (I'm a computer geek so I can say that, lol.) or have big rendering or video file conversion to do then you would probably be better of with just a faster single processor and lots of Ram. (not to mention a snazzy case with some lights and a solid game system underneath impresses the technoweenies just as much, lol)