Wow! So you got a really good deal, for amazing headphones. I was reading previous messages and I think that they should be a good complement for the 58x. I don’t know if the Denon 5200 are very different from the Fostex Ebony, but as far as I know, they should be pretty similar. Denon stopped using Fostex drivers, but I don’t remember which models exactly.
Keep us posted after you have used them more. Give us impressions compared with the 58x.
I am glad that you got such a great deal.