Whenever someone mentions classical music, I like to chime in with the following few recommendations:
William Orbit - Pieces In A Modern Style
Aria - Aria
Aria - New Horizon
The first is an interesting interpretation of some classical pieces in an electronic style. If you've heard any of William Orbit's solo work before, you know what to expect here.
The second two are electronic interpretations of opera arias. Not sure if people classify that as "classical", but I do.
