Oh! Me, me!!
Composers to check out:
Jacques Hetu: Canadian composer who uses ... well, it's what I'd call Tonal atonal music. See, he takes the ideals of tonal music and applies it to an atonal framework/harmonic language. He sounds a bit like messiaen, (maybe because he studied with him at one point?!). His music is breathtakingly beautiful and mysterious, with plenty of comedy and such. Highly recommended to check out his piano concerto, flute concerto, and whatever else you can find :P
Reiterating Messiaen and Higdon....
Eric Whitacre: More beautiful choral music I dunno if you will find. He is sometimes a bit cliched but he is amazing and his harmonic language is brilliant. I would say he is a Tonal Composer but he plays with tonality a lot. Similar to Part, really...
Christos Hatzis (spelling?!): Canadian composer who is quite amazing. Check out his choral works (Everlasting Light, (something to do with angels)), and his piano trio "Old Photographs" from Constantinople. Enjoy :lol:
Reiterate Lygeti (the etudes are hella awesome!), and part and takemitsu.
I could go on for ages... I love modern music...