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10926 episodes available for download in 578 titles
If you're into Speculative fiction... check out
The Leviathan Chronicles (or whatever else catches your fancy). It has a full-cast, sound effects, music, etc...
I've listened to a few episodes from several different titles, but audio just doesn't seem to be my cup of tea—as much as I wish it were—so I can't really vouch for the overall quality of the stories, but there should be something there that might work for you.