This site has alot of great info, and a car audio section. Amp design guru Nelson Pass is there as well(old school adcom, and soundstream I believe), with his own section that he frequents.

http://www.diyaudio.com/

and the LDSG has a massive list of driver reviews and info.

http://ldsg.snippets.org/index.php3
(click on index to get started with it)