I actually taught "A Seperate Peace" to a freshman English class when I was in college. It always seems to go hand-in- hand with the Catcher in the Rye. However, I think teachers and critics tend to get too caught up in all the psychoanalytic metaphors in A Separate Peace (this character is the id, this character is the ego, and so on). While this may be a valid way to interpret the story on a critical level, I think it works best as a story about making oneself whole. When we're young, we have boundless energy and a burning need to fill ourselves with ... something. A lot of that energy goes towards building friendships. However, since we have an unsophisticated and fluid notion of who we are, we're very impressionable to the strong personalities around us. They fill the voids we identify in ourselves. However, there is something disingenuous about simply transplanting the ideas and traits of others into our own makeup.
It rubs our sense of self wrong -- and eventually we reject those traits that most conflict with other ideas and notions that have a firmer foundation (such as family values or religious codes).
I think that's what Knowles was trying to expose -- adolescence is really a time of full-contact personality building. The friction between what our friends, teachers, etc. are telling us, and what we already know about ourselves eventually leads to a harmonized sense of wholeness -- a separate peace.
Based on the books and interests you mentioned, here are some poets you might like: 1. Elizabeth Bishop -- she is not commonly taught, but she was a U.S. poet laureate in the 50's. She has a wonderful way with words, and her poems often read like a dream -- elements of the real world and elements of fantasy.
2. Robert Lowell -- most often compared to Sylvia Plath because of their confessional styles, he is the superior poet by far. He suffered from manic-depression, and he often wrote about his experiences in mental hospitals. It is fascinating to juxtapose his poems, as they are blueprints of his mental condition. When depressed he turned inward (and wrote his best stuff), when manic he was all exuberance and colorful language.
3. James Dickey -- best known as the author of "Deliverance" and "River Runs Through It," he also had a wonderfully madcap style to his poetry. My favorite poem by Dickey is a long rambling exposition of the thoughts that might pass through an airline stewardess's mind as she is sucked out of an airplane and freefalls to her death.
As far as good vs. evil goes, the greatest by far is William Blake. It's best to have some knowledge of Biblical stories before attempting Blake. You might also like William Butler Yeats, possibly my favorite poet, who was as Irish as they get and developed a whole mythological system (taking from both science and religion) which he transferred into his poetry.
Give one of these poets a shot, and tell me what you think.