I'll be getting a Quad Core Opteron and an AM2+ motherboard. Probably pick up a cheap OEM Athlon AM2 CPU as well just to make sure I can get the board setup properly for the Opteron.
Any down sides to running an Opteron in an AM2+ motherboard, other than RAM speed? I know the Opterons don't support DDR2 1066 RAM, but that doesn't bother me. DDR2 800 or even slower RAM would be faster than the DDR 3200 in my current rig.