@Kay: I found out about them the same way, but I didn't even know that ready steady go was them until a few years after I first heard it and I realized that was hyde's voice lol
I didn't know those bands were active a decade ago. I think L'Arc!~en~Ciel is still together, I'm pretty sure dir en grey is. But I don't know about Uverworld and High and Mighty Color.
I shall give you some suggestions though =]
Jrock: GazettE, Kagrra, Miyavi, SuG, An Cafe, UnsraW (not sure if they're still together) Chemical Pictures, Sectmateria, Himeyuri, DIS Marionette, Ayabie
Jpop: Berryz Koubou, Koharu Kusumi, Morning Musume, C-ute, Kirarin Revolution (the group, not the anime), Buono, W, and Gyaruru. That's really all I could think of for jpop though, for jrock I could go on forever.
@JosephKT: I keep seeing you everywhere XD Did you listen to other visual kei bands before? I love dir en grey, they're the only band that I have an official CD of. But that's mostly because I don't usually buy CD's and up until just recently I couldn't find GazettE CD's locally. But now GazettE is getting more popular because they made the song for the opening of the anime Kurohitsuji. I think I'm rambling a little bit, sorry lol