Don't worry about being average... Remember that means that half of those admitted had scores below yours! But I understand that you're not totally happy with your quant score.
Still, though, I think you biggest challenge will be in putting together an app that stands out in some way compared to all of the other applicants who will have finance backgrounds. Instead of focusing on what you think will keep you out (in this case, it's your GMAT score that you're worried about), ask yourself, "What in my app will stand out and help me get in?"
That's how adcomms look at it (they're not just looking for reasons to ding people), and I recommend that you approach it that way, too.
Scott
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Co-Author, Your MBA Game Plan