Audition online is nice :) except that levels don't really matter. You can be a stiffy and still beat all the audition masters depending on how fast your fingers are or how good your timing is. Plus there are a lot of perfect hacks so winning doesn't really matter much anymore... that's the main reason i quit that game. It's really disappointing cuz i spent a lot on that game
I also tried Love Beat before. It's sorta like a mix of idate and audition. It's really cool unfortunately it doesn't have that much players as audition or idate... and i don't know if I'm just really used to fast songs because i played audition before, but i find the songs really easy.. also i can't find a "chance mode" in Love beat (which i hoped would make it more challenging). If it gets more updates, maybe i could play it again.
You can also try HighStreet 5 but im not sure if it's still running.