Welcome. We're a small but friendly forum. So, feel free to post or explore the topics here. (I'm starting to sound like a broken record)
Well, you watched the anime, so that's a great start. I would highly recommend playing the main games such as the most recent one being One for All on the PS3, which is region free. You can watch youtube videos for Idolm@ster 2 (which came before One for All) if you don't feel like playing it on the PS3. At the same time, check out other im@s stuff such as the music, mangas, drama cds, movie (not that great), etc if you feel like exploring more. We also have a wiki here, so check that out to read articles about everything for im@s franchise.
Unfortunately, I'm not a fan of puchim@s, so sorry about that.
By the way your Tokyo Xanadu topic is very interesting, and I would like to know who are the other im@s VA in it (I know one being Hibiki). But, we have a topic for games (it's the topic farther down which says games games games), so it might be more convenient for you to post there in the future.