Thanks for the submission. Don't feel like you have to stick so much to the main corporate logo. We want the logo to be unique and stand on it's own. A good example of this is Coldwell Banker vs Coldwell Banker Previews (their high end version). Here is a graphic that shows both logos. They are unique and easily identifiable as unique.
http://www.naplesarea.com/agent_photos/CBRR03_CB-Logo__Previews-2_NaplesArea.jpg