The opteron motherboard has an nvidia chipset. Board model is: nVidia DP Sledgehammer CRB
The Xeon boards are identical Super X6DA8-G2.
The Opteron boad has 8 sata channels and onboard IDE and is SLI capable.
The Xeon boards have an intel chipset and also have dual PCI-E slots, not sure if they do SLI. They include 2 sata channels, onboard IDE and onboard SCSI