I think any 939 with X2 support will support the Opteron. It's all "unofficial" since Opterons are supposed to be used with "server grade" motherboards. I have an ECS KN1 nForce4 SLI Lite (cheap, cheap), and my Opteron 170 works perfectly @ 2.97 ghz. KN1 SLI Lite doesn't have exceptional accolades (e.g. Newegg reviews), but I've been fortunate enough to have zero problems with it, excepting a BIOS update went awry (my fault, though ... )
I actually used a 165 in a Biostar Tforce 6100-939. It's not supported but worked--sort of. The only problem was there was no Vcore adjustment. BIOS options were only startup (1.35v) or 1.85v. 1.85v is just stupid. I guess it didn't matter that much because my 165 will do 300 HTT with stock volts. :lol: The mobo would go faster but needed more Vcore to get it stable.