In Search of J-pop

I've had a couple of good experiences with Japanese music, or J-pop, and I'm hoping to find more albums that I would like. It's been difficult finding good reviews or samples so that I can make an informed decision on what to try. I'm also having a hard time finding retailers that sell imported CDs. Amazon's inventory is pretty weak and most of the search results I get are japanese sites. I currently have Takako Minekawa and Nitro Microphone Underground. Any suggestions?