“Anandtech”:http://www.anandtech.com/guides/showdoc.aspx?i=2753 does another Buyer’s Guide. As he says, it is a hard time to recommend buying a desktop because both AMD and Intel are changing things so quickly. In a few weeks, AMD launches their AM2 platform. It isn’t any faster, but uses much cheaper DDR2 memory, so you should wait for that.
On the Intel side, they are going to launch their desktop “Core Duo 2”:http://www.dailytech.com/article.aspx?newsid=2170 in a July so this will be a massive increase in performance, probably outstripping AMD by quite a margin. While you can get the very expensive AOpen i975Xa-YDG and the Core Duo T2400, these are very expensive chips right now. [For you codename geeks, the desktop Core precoessor codenamed Conroe is now the Core 2 Duo, while the new notebook processor codenamed Merom will also be the Core 2 Duo,]
So the best advice is, if you can wait, you should do wait on the desktop side. If you can’t and want the performance then the Core Duo T2400 is the way to go.
