Since you say "low-end" Xeon, that rules out the Xeon MP and leaves only the Xeon proper, which is essentially a multiprocessor-enabled Pentium4. Unless the workstation is dual-capable and your apps, or combination of apps, would benefit a lot from running on a dualie AND you could talk them into buying the second CPU, then get the P4. The only other area where I could see the Xeon system making sense is if you absolutely need to use, say, 4Gb of RAM.
A P4 with Hyperthreading, using a HT-supporting OS such as WinXP Pro, could boost your multitasking performance. Then again, with WinXP Pro being about 10% slower than Win2000, you'll need the extra power just to run the OS...

The 3.06GHz P4 is currently the only HT-enabled P4 on the market.
If it were me I'd insist on building my own, of course

And it would be an AthlonXP 2700+ on nForce2, with large quantities of Corsair PC3500 RAM and 15,000rpm SCSI drives. To each his own...