Seeking advice for a quiet car!

My wife has been driving 2008 Acura Tl for 15 months 24k miles. She started to complain that the car is a very noise (road noise) and has a firm ride. Daily commute is making her tired. The other car is a 2002 Lexus RX300, which is not quiet either. We need some advice for a quiet sedan for around $50K. I used to drive Cadillac Deville, which is very quiet, but it is not suitable for women. I am think MB E350, but not sure it is quiet. Thanks a million!