The HD600 might sound a bit boring to you when unamped, especially when used for games and movies. I would look into a Beyerdynamic DT770/80 Pro, or maybe the 32ohm version of the '05 model. I believe either of these can be found for <$200, and I know for a fact the Pro sounds great with games. They are circumnaural closed phones.
Actually the absolute best can I have found for games is a properly amped Grado GS1000, but $1000 for a gaming phone is a little extreme.