heya christmas;
Unless you are going to be crunching data 24 hours a day you dont really need a dual xeon core, a single P4 will do just fine, both the P4~533fsb and P4~800fsb are strong CPU's they will do the job. Dual Channel Memory Mode is where you will see the most gain, make sure and get an motherboard with an Intel i865, i875, or i7205 chipset, and if you are just hard set on going dual xeon get a mobo with a i7505 chipset.
If you have any further questions, i will be around.
XeeN