I can't speak for good - I have been doing my own. However, I have 3 in my favorites list. The first two I have bought products and components from, and gotten very good service. The 3rd one I have seen ads for the magazine for years, so he must be doing something right.
DCC Installs and Sales, Marinez Georgia, really nice guy
http://dccinstallsandsales.com/index.php
Tony's Train Exchange, A large outfit. This is retail arm of American Hobby Distributors.
https://tonystrains.com/services
Litchfield Station, I have seen ads for years
http://www.litchfieldstation.com/
Usually there are ads for a half dozen or so in the various modeling magazines.