What's your budget?
Have you considered one of the many Asrock boards that are meant for transitioning from old to new technology? For example, this board
will allow you to run a Core 2 Duo CPU, either DDR or DDR2, and either AGP or PCIe. So, you could use your old parts, then upgrade the RAM and video at your leisure. Keep in mind though that the PCIe slot is only 4x.