I love what Zizek says about atonal music. I think he is a closet Schellingian who only believes he is a Hegelian, personally. He writes so incredibly well in that mode.
So I'm listening to Stockhausen. I don't have everything he did by any means but I've been into it since I was 12.
The HMV chain is having trouble in the UK. When I was 12 I used to go down into the basement of the Oxford Street store and pour over the contemporary music as if it was from another world (it is). The smell of the vinyl and the plastic sleeves the record sleeves came in.
My first purchase from there was Stockhausen's Mantra. Still amazing to me.