You want to go 2000 Pro.
2000 Server is not the same as 2000 Pro. Many companies that handle video graphic, sound cards, printers, handheld computers, etc. are not aiming for the 2000 Server version.
A server is aimed to please a work house on the CPU, memory and harddisk. For example; graphics are not a must on a server vga mode at 640 x 480 is more then needed for a server.
Bottom line drive drivers are not written for 2000 server, besides those that are going to drive the CPU, memory and harddisk controller.
Plus there are a ton of programs that are running in the background for a support of the server and may slow down speed for games and hardcore multi-media applications.
If you are just using it to run Word, Excel and couple of other normal applications then stick with 2000 server and save your money for beer.
If you are running graphic programs, CAD programs, music software, Napster (or somthing like it), I would say 2000 Pro.
In my opinion XP is a far better program to 2000 pro by a long shot.
I run 2000 Pro as my Game server and it is very stable, however I am only running one program at a time. XP handles device drivers much better then 2000 can.