Well, I know open back is really helpful with gaming. I don't hardcore game myself, but I know gamers really make a big deal about hearing where sounds are coming from in FPS games etc.
Be aware you will give up a wider soundstage with closed headphones. But isolation (and almost always bass) is better with closed.
My philosophy is to have fewer pairs of much more reasonable headphones, vs that one "killer" pair that is hundreds of dollars. That way, I can wear a portable/more compact/more isolated pair when out and about, an IEM when working out, an immersive pair for watching movies, a pair I can leave at work on my desk, and a nice pair for critical listening sessions at home (with disregard to how big or ugly they are, and whether they fold up or not).
The HD558/HD598 are really nice headphones for many of the above situations - games, movies, listening at home, at work. Just not working out or wearing when out and about.
I really like Philips headphones (in general). They continually surprise me with their clean sound, quality construction, and incredible value for the money. They are always on my list when I'm shopping for a pair of headphones (open, closed, whatever).
Since you also have the restriction of needing to buy a headphone locally at a shop (vs amazon/ebay/etc), that seems like it's going to influence your decision above all else. Why don't you let us know some of the models in stock at your local shop (and in your price range), and we'll try to make a recommendation from that more narrow/manageable list? Otherwise, you could get 100 recommendations from 100 different people, where none of it applies to you because they're not available at your local shop.
