Without trying to be rude, the Sennheiser HD595s are OPEN. So when someone says "closed cans only" and recommends the 595s I would personally question that resource. No offense to anything being said, but I would like to point that out to the original poster.
Some questions I would think you'd want to know before making a choice:
1. Do you want to listen to music at all or do you simply want to have a very clear, precise set of headphones so you can hear where things are coming from?
2. Do you need an amplifier for them?
3. Do you plan on playing games in a quiet room or around potential noise interference, i.e. a LAN party or obnoxious air conditioner?
4. How much do you really want to spend to get "the best"?
I know you have perhaps answered these questions, but they are very important to lay out to yourself. It is very easy to get lost in these forums with everybody posting wild ideas and one-up-manship, leading to you either blowing your budget completely or being more lost than before. Get what looks best to you after looking at what others suggest. Make sure the seller has a way for you to return any items you buy if you find out they aren't right for you. If possible, try to listen to as many pairs of headphones as possible before making a decision. Remember, it's your opinion as to what is best.
I will be fully honest and say I am not a competitive online gamer what-so-ever. I bought a pair of HD650s entirely for music. Do I do a bit of light gaming? Sure. Are they perfect? I have no idea. I doubt it, but I'm not going to go spend every dime I've ever made to find out. Personally, I would think that if you plan on playing in a location away from loud noises, a proper open headphone would offer the best soundstage/ clarity, but I know that there are closed headphones that compete very well. There are many threads about this topic, so try a bit of searching before trying to make a be-all, end-all purchase, because that isn't going to happen.
I realise this probably isn't the most helpful post ever on the topic at hand, but I want the original poster to understand that you need to take everything with a grain of salt. There are no facts about audio, at least not ones that are of any benefit. Some people here will tell you that your power cable will affect your sound. Others will disagree. It's the nature of the beast. My personal recommendation for you is the Beyerdynamic DT770s or the Sennheiser HD598s. I've seen both recommended highly for gaming and should be enjoyable for music too. Obviously you're smart enough to do research, so when you do buy something, enjoy it! If it meets your standards, then who here is right to tell you you're wrong?
