Do Ghz Really Matter?

I am in the market for a new AMD CPU for my board as the older higher end chips for it are becoming much cheaper now. I need to Know if a Faster duo core(3.0Ghz,3.2Ghz) would be better/worse than it's slower quad core cousin(2.4ghz,2.6Ghz). These are the fastest in each respective catagory for my board. Any help or opinions is greatly appreciated.
Specs below:

Specs below: