I got my ATH AD900s at Sound Pals in DenDen Town! There are a few great hifi shops thereabouts. Also, be sure to stop in at Yodobashi Camera in Umeda because they have frickin' everything (it's a good place to pick up cameras and electronic dictionaries, too... but they havea good sound department). I don't know about now, but they had some L3ks on display 4 or 5 months ago. You can snag some Eggos or some FC-7s at least while you're there. You'll also have the unique chance to audition all of them at once because every shop worth its salt has floor models for most of their headphones. A lot of places will have the full non leather or wood AK line out to listen to, along with sony, akg, sennheiser, and koss. I've also seen fostexes and pioneers. One of the shops in denden town even has Staxes out to audition. I would recommend going to Sound Pals first because they are small, and quiet (you won't get this auditioning headphones in yodobashi). And I got a super deal on the AD900 there. 200 bucks new!
You might check shinsaibashi as well if you want to see some hip clubs/clothing stores. There are some really good restaurants there too. Gotta do kaitenzushi, mos burger, and especially okonomiyaki if you get the chance.
Sorry to ramble. give us an update with what you get/pictures of strange things you eat. I'll post anything should my memory be jogged.