You may find the following material useful for this topic:

• Gate Control Theory (an overview of many of the topics you have covered)
• Systematic reviews on pain :Kenny Jackson list of all systematic reviews on pain (up until 2004).
• University of Bath pain links: A thorough set of links from this recognised department. 
• Liverpool University Pain research unit: The Pain Research Institute is part of the University of Liverpool, Department of Neurological Science. The Institute carries out research into the causes and treatment of chronic pain in humans.
• International Association for the Study of Pain (IASP): IASP is a non-profit professional organization dedicated to furthering research on pain and improving the care of patients with pain.
• The UK Pain Society: The Pain Society is the representative body for all professionals involved in the management and understanding of pain in the United Kingdom. The Society aims to achieve the highest possible standards in the management of pain, through education, training and research in all fields of pain and by facilitating the exchange of information and experience.
• The Oxford Pain Internet Site: This site is for anyone with a professional or personal interest in pain and analgesia. It is firmly based in the principles of evidence-based medicine and has pulled together systematic reviews with pain as an outcome.
• Back pain guide: Provides a good, introductory overview on the models of pain.