I've not bought from lots of different vendors to come to this conclusion - but just in talking with these folks (and a number of excellent parts purchased) I'm supremely comfortable with them.
SNG Barratt:
http://www.sngbarratt.com/Home.aspx?b=US
Download their catalogue here:
http://www.sngbarratt.com/DownloadArea.aspx
The guy that I happened to catch on the phone the first time I ordered something was so knowledgeable that I keep calling for him when I have a need:
Frank @ 1-800-452-4787 Extension: 212
Good luck!!