I'm thinking about a new server, something with dual CPUS, but I don't know much about hardware. I see there's choices to be made:

Dual Xeon Vs. Dual Woodcrest Vs. Dual Opteron Vs. Dual Xeon Dual Core

Any suggestions? Is there something to know about each processor that makes one much better than the other (and worth paying more)?

This is for a general purpose web server, blogs, wikis, html, some email, etc... from a few hundered domains.

In my opinion, the progression goes from -

Dual Xeon (Single Core, Hyperthreaded) > Dual Opteron (Dual Core) > Dual Xeon (Dual Core)

Please note, Dual Woodcrest = Dual Xeon (Dual Core)