As you've asked Paul, I can recommend some gradual immersion into the Bill Schuman symphonic series, now being well recorded by the ever-brave and never-lacking-initiative Naxos label.

Try Symphony No.3 as a start, and a shorter, lighter No.5 (for strings only) to be going on with. Both of these are on a classic Bernstein conducted Columbia CD from the '60s. He had abandoned (i.e disowned) his first two, so these have seldom been heard at all. His oft-heard orchestration of Charles Ives's arrangement of "America" remains one of his few popular works, and is quirkily amusing and justly revived every so often.

All his surviving symphonies are on disc (no complete cycles so far) and all 8 are worth sticking with.