J.D. Power and Associates is best known for their ratings on cars, electronics and other products. But for the past two years, they have also rated the top real estate brokers. In the study released this summer, Coldwell Banker was the top-rated agency for home sellers. The 2009 Home Buyer/Seller Study includes more than 3,100 evaluations from 2,801 respondents who bought or sold a home between April 2008 and June 2009. The study was fielded between April and June 2009.