http://audiotools.com/a.html

A is a good place to start.
When looking for info on car audio I came across the above site.
Basically it lists most of but not all the Audio manufacturers and shows the linked companies.
Interesting for when you see or hear of an unknown brand or to check the credentials of a touted decent brand.

I now know that Denon and Marantz merged in 2002 to form D&M Holdings and then this company purchased McIntosh from Clarion in 2003.

Might be something that helps pass time if you are bored.