Wagner, Beethoven, Sibelius
I just listened to Gerhard's 2nd SQ as well (Arditti). This quartet is very interesting to listen to (I particularly like the last "movement") and I find it fairly easily approachable even though I haven't quite warmed up to the modern sonic idiom Gerhard uses. One can even hear that he was acquainted with Schoenberg. I like such works as they help a lot with getting better acquainted with music I'm generally not so comfortable with.