(Re. the NetBSD/amd64 portion of your question.)

If by "Opteron", you mean technically the Opteron CPU (as opposed to the
other AMD64 CPU (Athlon 64, or whatever)), I'm not sure.  But if it
has a PCI or AGP slot, I think that the same cards as work with i386
would work with AMD64 for X servers.  (I don't know about laptops or
others with motherboard video.)

If you mean to include the "low end" AMD64 CPUs (Athlon 64, or whatever):
I would suggest avoiding nVidia nForce3 based motherboards.  (I've ranted
about that before, though.  (^&)

Pre-2.0 -current, or 2.0+ releases should run well, as far as I know.


Just my 2.718281828459045... cents.

-- 
  "I probably don't know what I'm talking about."  http://www.olib.org/~rkr/