Seeing as the main focus is a lan gaming box i figured i would see if a HD5850 would fit + work. After a bit of research it seems it will fit "just" but that + an 860 is probably bad news. Solution? i5 dual core i reckon.
Add the OCZ platinum RAM at about £85
Edit - and a slot loading DVD Drive (just ofr the cool factor)
Just to reiterate its main function is a lan gaming box so a dual core would probably be just as if not more appropriate for most games.