Do you have a lot of money invested in nikon glass? if so, dont even bother with the 5d.
Is there a reason why you want to replace the D200? doesn't make much sense if you just want a nice camera since the one you have is pretty nice already. I would suggest you list some of the lenses you have and I can suggest some killer glass for you.
If you still want to upgrade your camera body, i suggest going to a henry's and try it out. Without a doubt, the Nikon pro bodies have the best feel to them.
PS. I have a 5d and its my workhorse, if you ever wish to switch to canon, and money is not an issue, thats the way to go.