Other car Audio Forums
 

http://www.clubknowledge.com/Car_Audio_FAQ/forum - There are some very experienced installers and techs at this site. They don't sell any products, so there's no incentive for them to recommend one brand over another, other than quality/value/personal experience. It's a well moderated site that doesn't allow flaming, profanity, or personal disputes..

Re: Other car Audio Forums
 

http://www.elitecaraudio.com/

Very knowledgable. Just beware, most serious competitors have sponsors and are slightly biased, but they do the best they can to be honest about recommendations. If you have very technical questions, I mean VERY technical, this is the place to go. Most of the editors are EE's.

Re: Other car Audio Forums
 

www.caraudiotalk.com

First forum I ever joined...still there.

Please don't join www.caraudio.com They are a bunch of retards over there