The difference between the D2X and the D2Xs is really very minimal. The biggest difference is the D2Xs has the viewfinder masking feature when using DX crop mode, the D2X only has the rectangular box in the viewfinder. Most of the other upgrades were added to the D2X via the latest firmware.
The AF system is the same as your D2H. Noise can be an issue at ISO 640 or so on either body.
If you shoot low light sports you might want to consider the D300 or even the D7000 as suggested above. Both have better AF systems and high ISO performance. Good Luck and Enjoy your Nikons!