the D820 looks a little thinner than that and it's listed as a desktop replacement so you can't ask much. I like the extra room inside for working on it as well.
My D810 managed around a 2300 with the stock x600 overclocked well within boundaries and everything else as it would come from factory. Can't remember what I got with it setup the way it is in my sig though. I'll have to bench again later now.
Edit: Went and benched and at 350/355 I managed 4434 3dmarks