The missing emblems could mean it was rear-ended. Even if the carfax is clean, look over the paint. Inspect between the rear door and rear quarter panel as well as rear quarter and rear bumper. Have a look underneath to see if a new exhaust has been installed from the axel back.
Keep in mind that carfax may not have the most up-to-date information available. If the car was recently in an accident, it might not show up on the report yet.
At the price they are asking, expecially considering it has navigation, i'd be blowing the too-good-to-be-true whistle. But I could be wrong...in any case, haggle for the best price and make sure they throw in the 30k maintenance.