Right now, not many programs utilize more than 2, and only a handful of games can utilize more than 4. If you needed to do some heavy computing or want to game on high settings you might want the 8core, however, the 6 core can be overclocked and is nearly half the price.
Personally I'd get the 6core because it will work great for games and be cheaper, that way when and if you HAVE to upgrade, you will be at less of a loss.
Look at Tom's "Best Gaming CPU for the Money September" I believe the 6300 is the pick for the $120 range, it's a good deal. Hope this helps.
Here is also a build I did for a different thread but your budget is around the same.