I like those for high end and used gear. Bigboss is good for anything affiliated with ESP.
Start scouring digimart.net for gear before going. Just use a translator extension in you browser. You can get an idea of sore inventory and do research before hitting the stores.
Lastly, most of the prices include a 10% sales tax. While haggling is frowned upon in Japan, it is absolutely reasonable and i encourage to aske if they can discount the 10% tax if you show them your passport. Some will do this and some wont. ASK