Alrightey! I don't own any of these CDs, so can't vet performances or curation of collections, but I know many of the pieces and all the composers, and enjoy them myself. I'm skipping names popularized by Kubrick.

Hopefully you'll find one or two to suit.
Some 20th Century "easy listening":
Lili Boulanger (sort of her "greatest hits")
All eight symphonies of Einojuhani Rautavaara (his concerti and "Cantus Arcticus" are also highly recommended)
George Antheil, "Orchestral Works Vol 2" ("Archipelago" is amaaaaazing, and I assume you have "Ballet Mechanique")
Ned Rorem, "Three Symphonies"
...And more meaty fare:
Selections from Sofia Gubaidulina (all of her work is great - check out "Concerto for Two Orchestras" on YouTube for a real treat)
George Crumb "70th Birthday Album" (I'm guessing you already have his "Ancient Voices of Children." I turned down a chance to meet him because I was chicken)
Penderecki, "Symphonies & Other Orchestral Works" (a bit of a mish-mash)
William Kraft, "Contextures" (yes, he scored Bakshi's
"Fire and Ice"!)
Olga Neuwirth, "Lost Highway" (an opera based on David Lynch's film)
...For wind ensemble:
"Composer's Collection: Joseph Schwantner"
Persichetti, Collected works
In the vein of Philip Glass:
Meredith Monk, "Do You Be" ("Turtle Dreams" looks to be out of print)
Julia Wolfe, "Anthracite Fields" (I prefer her "Arsenal of Democracy," but can't find it)
...And some chamber stuff (heavy on the Manchester School):
Harrison Birtwistle's "The Moth Requiem" (and why not pick up the DVD of his opera,
"The Minotaur"?)
Peter Maxwell Davies (RIP), "Eight Songs for a Mad King" (or anything by him)
"Jennifer Higdon: Chamber Music" (I met her once; she's neato)
Wolfgang Rihm, "Et Lux"
Kaija Saariaho, "Trios"
Okay, so this isn't modern, but Gesualdo's music is...weird for his time, so it almost sounds like someone today mimicking Olde Musik, but...
Don Carlo Gesualdo, "Complete Madrigals"
Amazon's coming up empty on a few others, like Gaziza Zhubanova, Betty Olivero, Andrew Norman, etc., but hey, there's always YouTube.