I've done 1DII & 7D at the same time. I sold the 1DII. The 7D is just better in every way. It even has great weather sealing if you care about it. Better batteries by far too. I think the 1D3 at the same cost of the 7D is more of a competitor, but even then, the 7D just offers more. The 1D3 is if you want to shoot with muddy hands or in the sprinklers without covers at all--but weather resistance is totally a moot point unless your lens is totally weather resistant too, so this is a big argument to just not worry about it since this is obviously about budget and there's no weather sealed budget Canon lenses. Heck not even all the L's are weather sealed (crazy...). So 7D just makes the most sense.
1Ds II would be the full frame 1D that is affordable and still relevant. But, at 4 FPS, this is not for "action" as much as the other cameras you're looking at. This is if you want a 1D level autofocus system on a full frame sensor on a budget. Just remember, old batteries, small screen, super antiquated menu system and only 4 FPS, on a 1D body, at about $600. I almost went with this, but the batteries and 4 FPS killed it for me (already owning 1D2 and 1Dc).
For cost, 1Ds III is out of the question in my opinion.
Edit: dangit, October thread...