Nick,
I know it has already been suggested, but I also vote for a Canon 5DSR (or a 5DS). I shot extensively with a 5D Mark III and then recently moved to a 5DSR and a 1DX Mark II. I have to say, the 5DSR is a really, really nice camera. I am very impressed with it. Take nearly everything the 5D Mark III has and improve on it, and more, and you have a 5DSR. The detail is truly fantastic.
The only things to be aware of regarding the 5DSR is that you will need more storage space for your files, an up-to-date computer to process the files, and high ISO performance will be slightly less (before you take into account any post-processing tricks). However, in exchange for these considerations, you get a ton of increased benefits over the 5D Mark III. Way too many to list here.
If money is a deep concern, then yes you can pick up a 5D Mark III and have $1K leftover for another lens. However, the 5DSR is an amazing camera that will give you so much more than a 5D Mark III alone.
Just my two cents. Of course, there are other options out there.
Cheers,
Bryan





