Reading about what you already know (sort of).

Recently I was trying to defend my practice of reading the classics by arguing that there is significant value in actually reading works which are a fundamental part of our culture and which are often referenced, even if we are already roughly aware of what's being referred to. Is this just a rationalization for pretentious reading material or do we need to immerse ourselves in Beowulf to fully grasp what someone means when he throws out an allusion to Grendel's mother? Would one be better off reading some new masterworks that haven't yet percolated through the collective subconscious?