Every time I hear Debussy's first arabesque, I will always think of the stars.

As a non-casual "classical" listener, I can heartily recommend the Naxos Music Library. This is a little different from naxos.com suggested above: naxos.com only has recordings from the Naxos label, while the NML includes many sister labels (including some great ones, like Wergo). They add about 1000 CD's every month, about 40 a day. I've rapidly expanded my knowledge of new composers, and great recordings of old composers. They have multiple recordings of the Ligeti string quartets, including the Arditti Quartet, for example. They're not cheap, though. :(