peer review

Hi all,
I am a SoC student, I'm developing a new peer review based system for discussions.
My project is highly based upon stackoverflow.com model which uses a Karma system based upon votes.
Drupal has an interesting User Karma (http://drupal.org/project/user_karma) module, which is not exactly what i wanna do, in fact it is best for digg like websites and is developed for systems like them.
I have to develop something that is different, something that enable me to count votes, subtract votes, and make particular stuff using specific rules.