you wont need a 2k3 box in your CEH lab, there are practically no exploits for it.
you are best off with a Win2k and WinXP box for your windows victim hosts
i would suggest a linux victim box as well, like RH 6.2 or 7.2, something with lots of exploits so you can explore the ins and outs of popping a shell, and then what to do with that shell on both types of OS'es
i would also recommend a linux and windows attack host, XP or 2k for win, and backtrack should suffice for your linux box.
i'll put the caveat that i am not a big fan of backtrack because the majority of your linux skills come from installing all of the software and dealing with recompiling the kernel and dealing with dependency issues, its a good "tool" but urks me when someone says that their primary linux OS is backtrack.