Detail is great across the board, but not harsh because of the signature/temperament of the HD650s. Staging probably isn't as big as some other cans, but it's plenty big enough to give solid positioning information. I was using it in ME3 multiplayer and finding myself turning towards sounds before I even realised what I was doing - very lifelike and realistic imaging.
I've found something interesting on Borderlands 2 though which is that sounds which should be in front seem to come from behnid (or vice versa - can't remember). Pretty sure this is in the game's 2 channel sound output so not an HD650 issue, but need to test with other cans to confirm.
Go with the HD650s - they're so perfect for music and really good for gaming, plus they're generally super comfortable and non-fatiguing no matter what you're doing.