Thankyou for your response to my question about lui with the entendre parler construction. I have done some reading and I think that I understand your answer now. Some verbs (like parler) just require the "de + stressed pronoun" rather than the typical indirect object. If, with this subset of special verbs, one wants to replace the stressed pronoun, the replacement is with "en." So "J'ai entendu parler de eux" would become "J'en ai entendu parler???"