I love classical music but with the exception of John Williams, Scott Joplin, Aaron Copeland and the Gershwins, most modern classical music stinks. At least to me; YMMV.
It took a while, but their music has really grown on me, in an autistic sort of way, and I particularly like Adam's Nixon in China opera.
If you really want to mess with your mind check out Gavin Bryar's monumental Jesus' Blood Never Failed Me for a great minimalist modern piece (with Tom Waits). I ran, did not walk, to buy this after hearing in on the radio. BTW, I see that you can preview parts of this on Amazon.
Bryar's Sinking of the Titanic is also noteworthy.
An very good read for 20th Century ‘classical’ music fans is “The Rest Is Noise: Listening to the Twentieth Century” by Alex Ross.