I does sound like splendora on the daria move theme song, but there are indeed a million and one bands with the same vocal sound as splendora. I am relativley sure that the band is based out of NYC and I never see them on the club circuit. It seems kind of unlikely that a band that hasn't released an album in 5 years and isn't very visible in the NYC club scene is still together at this point. It's possible, but I wouldn't be shocked if it isn't them on the movie.
If anyone has any information to contradict what I'm saying, feel free to set me straight.
Reiss