Systems

All Car Stereos
Offers information about speakers, subwoofers, midrange, tweeters and crossover, and links to reviews and forums.
http://www.allcar-speakers-subwoofers-amplifiers.com

eBuying Guides: Where to Buy Personal Systems
Concentrates on where to buy and shop for products, but also has staff-produced buying guides for over 200 products. Some of the guides are links to other buying guide sites. Accepts no payments for listings.
http://www.ebuyingguides.com/where/persSys_w.htm

Epinions: Complete Audio Systems
Consumer-generated reviews, buying tips and advice, ratings, price information, and searchable in a variety of ways from price to product type.
http://www.epinions.com/elec-Audio-Systems-All