As someone who owns both a 5D(mk2) and the Fuji XPro-1, please try the Fuji to see if the quirky handling suits you. It's a superb camera, but there are things about it I hate. I bought it without trying one, and whilst I have adapted to it, it was never close to being the 'digital Contax G2' I had hoped...
As to value? I had a 17-40/4L and sold it for £325 which was a little too cheap. £350-400 seems right. The 5mk1? I'd suggest around £400 perhaps?