Contemporary composers. Please help.

For something new to the list I would add Hindemith specifically his Symphony in E flat conducted by Bernstein
and two Ballet suites The Four Temperaments and Nobilissima Visione

Charles Ives's symphonies 1-3 with Bernstein if possible

Khachaturian's Spartacus and Gayaneh conducted by Khachaturian with the Vienna Philharmonic

Given the OPs listed favorites, I'd suggest Peteris Vasks, Kalevi Aho, and Aullis Sallinen. I also second the recommendation of The Ligeti Project Vol. II on Teldec.

Schoenberg's Verklärte Nacht and Gurrelieder are late Romantic works, which may or may not be to your taste. I would however urge you to hear the Chamber Symphonies.

I hope the thread does not get off topic, with every composer who lived into the 20th Century being recommended.

Poulenc, Del Tredici (Final Alice), Bernstein, Prokofiev, Elgar, Sibelius, Menotti. . . among others previous mentioned.

Wow!!! Thank you guys! Thanks for such a great response.
I'll try to pick as many as I can. Some titles I aready have, so if you guys don't mind, I'm going to share some impressions to more properly defy my sphere of interest at this moment.

Thanks again.
Sergey

I'd like to mention Britten's string quartets. This maybe heresy, but I prefer them over Bartok's quartets. I like the Belcea Quartet's recording of these works. Also, check out Jennifer Higdon's piano trio and look for her violin concerto for which she won a Pulitzer today I've been told. I heard this work premiered by Hilary Hahn in Indianapolis and it is a very worthwhile piece of music.