I DID give him the link from ZipZoomFly.
The Opteron is an overall better CPU [currently] than the Athlon 64. When compared to the X2 3800+ (I went Dual Core beucase it looks like you're going to be doing intensive stuff) the Opteron has twice the L2 cache which is always a good thing. But the area where the Opteron really shines is Overclockability. The 1.8Ghz Opteron 165 has a very good chance of reaching 2.6Ghz. That would essentially make your performance equal that of a Athlon 64 FX-60, the "strongest" processor currently avaliable for the Desktop market. Not only that, but they're also put through greater stress before being shipped out, so you know its reliable.
There are no compatibility problems either since the Socket 939 Opterons are what we're talking about, and thats the same socket that mainstream Athlon 64s fit into.
So the Opterons are, in every way, better than the Athlon 64s.
PM me for Overclocking Guides
They're excellent and they're what taught me to overclock.
And that list that I made, its perfect, don't change anything in it.