How Do I Find This Info...About Bigger Pitched Companies

Ok I was scanning through blogs tonight and saw several big companies like audiovox, rca and so on and I have tried in the past to contact these companies from there main site with no response. Recently I noticed some bigger companies have another PR company that handles there media department... so how would I find out who takes care of the companies like that to pitch too? I know some mention the info in there post but not all and a friend let me know that much.. any ideas? Anybody already pitch companies like vtech, audiovox and so on that could help me out.....