to choose a earphone / headphone is very subjective, depend on your personal taste.
Some like heavy bass, some like wide sound stage, some like clear vocal.
Tell the staff what u prefer, they should able to recommend you a good one.
Can audit few earphone, headphone that intro by the staff.
Remember bring your ipod with your favorite song / music.
Some headphone / earphone required burn for good 100 hours. sound getting better after period of using.