Mike, have a look at the review of the D200 in this month's issue of Professional Photographer - the verdict is that it makes more sense that a D2X for many people.
I can only speak as a Canon user but here are some assembled thoughts:
1) Don't be put off by the D2HS's low pixel count - as I gather, it's similar in ability to the 1D, which is astoundingly good for 4MP.
2) I would suggest that you make every effort to try them all out on a moving target. I briefly had the 20D before moving on to the 1D and 1D Mk2. The difference in quality between 20D and 1D Mk2 is negligible but the build quality, shooting rate and more importantly focus speed and accuracy are miles ahead on the pro body. I suspect you'd find the same with Nikon's line up: the real test of the D200 is not image quality, but AF ability.
3) I'll preface this one by saying that I have no right to tell you how to spend your money, but... Don't bite off more than you can chew. At this stage in your prospective career, only buy equipment that you can pay off quickly. If you're able now to charge money for your services rather than supply photos in return for a press pass (and charge enough that you're not undermining the photographers around you) then go for what is affordable. If that happens to be a D2X then all the better
