hehe ya. Well you can get am2 boards cheap and a smidge more gets a am2+ board. A REAL AM2+ board that is which is only AMD/ATI chipsets right now. The Nvidia ones are am2+ compat which means while Phenom quad will run you dont get HT3, or the advanced power saving features nor PCI-e 2.0
Am2 boards are $50 and up.
Am2+ around $80 on average
DDRII ram is FAR cheaper then DDR so the upgrade IS justified add to that the cpu cost on am2 is lower. So if it were me Id upgrade mobo ram and cpu. A good dual core is $50 and up, ram same, mobo same. So for about $150-180 you could be upgraded. A 3800+ x2 is the cheapest dual core. Was $57 last I looked.