What's the best Bang for your Buck for AM2?

I recently had the luck of aquiring a MSI K9N Diamond Motherboard
http://www.pricegrabber.com/p__MSI [...] ...rch=MSI

I was originally planning on going Core 2 Duo, but Fate dropped me that motherboard so I was wondering what is the AM2 processor to get now at a reasonable price?

A well overclocked 4200+ can beat a E6600. I would stick with AM2 because almost any board you get for Conroe will very probably have compatibility issues with the quad cores, while with AMD is a drop-in situation.
Definetly the 4200+ has the best $/performance, I would use the extra money in a good aftermaket HSF like the ARCTIC COOLING Freezer 64 Pro and some thermal compound, Ive heard the Artic Silver Ceramique has detroned the AS5.