98 is fastest In my opinion but due to your conifguration I would say you would be better with 2k.
Only use Win 2k though if you are willing to patch to sp4, win 2k is only slow (As stated above) if it is unpatched i.e. SP1 or original release, the sp's make it much faster and due to it hogging much less system resources than XP your machine should run much faster.
Off Topic: I typed this in my living room from my NEW laptop on the wireless network, this is my first of mny posts from it
