Either choice, E4300, or E6300, you cannot go wrong. Those two are currently balanced in price/performance terms. The only way you can go wrong is getting a brisbane OEM at 69$. why? you still have to buy a cooler, and when you do, the price diff between E4300 RETAIL on newegg and the brisbane + cooler is around 10$.
IF THE BRISBANE WAS AT 69.99$ RETAIL, IT WOULD BE AN UNBEATABLE BUDGET DEAL!
E6300 is the obvious way to go for a step up eventhough admittedly I'm not trying to build a top-of-the-line system. It just makes the most sense. I think that even if the 3600+ were free, I'd still go E6300.