I've been going with 5Dc for some time now, got it around 450 € second hand. If you aren't a professional, I wouldn't put my money on the bodies, and I don't know whether there is that big a difference between 5D and 5DII.
My worst deal ever was to buy 20D new. Now I could only get about 10 % of the price I paid back, and this hasn't changed. I don't want to buy 5DIII for that reason only. If you plan on using 5DII, be prepared to sell it after 5DIV or 6DII comes out, that way you'll probably get most of it back.
Currently I'm just using 5D and 20D until they break, after that it will be the next cheapest FF frame available.