I just put together a dual Xeon rig, unfortunately I can't help much with what CPU they are comparable to. I think, and keep in mind this could be completely wrong, but I think they compare to the same clocked P4, only the Xeons are multi processor capable. If I could run sandra benchmarks to help you out I would, but it wouldn't help since mine utilizes both processors, it wouldn't be fair or possible to compare them to P4's using sandra. Hope this helps, but I am sure someone else can provide a more clear answer.
Edit
id you just change your avatar. I thought it was one thing when I started posting, then when I finshed it was something else, but maybe I am just crazy.