First of all,try to learn how to distinguish between the original and the dupe.There are numerous forums which discuss the thing(just google).Then,go to pentamenaka.In the first floor(starting from one near the stair),u will find shops (right side from the entrance) selling ep 630 or 635.U can get them for a cool 800-850 bucks.
PS: They usually allow u to check the audio quality on the spot and then determine whether to buy or not.U could probably bring one decent headphone for comparison(like hpm-70,not much difference in audio quality).