Given what you've listed, here are some works by other composers that you might like.
Debussy: Afternoon of a Faun, Pelleas et Melisande, Images pour orchestra, La Mer, piano music (esp. as played by Ivan Moravec)
Chabrier: Danse Slave, Espana (Ansermet or Paray)
Charpentier: Arts Florissants (Christie/Les Arts Florissants)
Corelli: Conc Grossi, op6,1-6 (McGegan/PhilBarO/HarMundi)
Rutter: Gloria
Dvorak: Serenade for Strings (Marriner/ASMF), Symphony #9 (From the New World) (Kertesz/LSO)
Grieg: Piano Concerto (if you liked the Rachmaninov...)(Boult/LSO, Curzon -pf)
Handel: if you enjoy Vivaldi and Bach's Brandenburg Concertos, you might try exploring a little Handel. Try his Water Music or Music for the Royal Fireworks (I like performances by Pinnock and by Gardiner with period instruments, but Dorati is good on Mercury in the Fireworks)
Kodaly: Hary Janos Suite (Kertesz.LSO), Galanta Dances (Kertesz/LSO), Peacock Variations (Dorati/PhilHungarica) - if you enjoy large scale Rachmaninov, the Kodaly will be worth exploring.
Nielsen: Saga Drom, Symphony #5 - worth a shot if you enjoy some of the others listed here. (Horenstein on Nonesuch)
Poulenc: Gloria, for Soprano Solo, Chorus & Orch (Pretre/FNRO, Carteri on EMI)
Prokofiev: Scythian Suite (Dorati/LSO or Skrowaczewski/MinnO, Lt. Kije (Reiner/CSO)
Ravel: Alborada del Gracioso, Pavane pour une Infante Defunte, Ma Mère l'Oye, Valses nobles et sentimentales (Skrowaczewski/MinnO or Paray, among others)
Gershwin: Since you like Gershwin, try the EMI recording with Andre Previn and the LSO for Rhapsody in Blue, American in Paris and Piano Concerto in F for luscious performance in an excellent recording by the two Christophers.
Bach: For the Brandenburg Concertos, try Trevor Pinnock and the English Consort on Archiv. For additional music by Bach, try his Triple Concerto, BWV 1044, with the same forces. The Violin Concertos are well worth exploring (BWV 1041-1043).
I am assuming you've well explored the music of the composers you've listed, but if not, we can offer some suggestions for additional music from those composers.
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