+1 for Speedzone. Raymond is very good at what he does. I have been going to Speedzone for about 6 years.

 

good friend of mine owns a small shop in walnut creek...called stereoguyz, http://stereoguyz.com/

he has been installing/building custom systems and car alarms for close to 10 years. he is crazy fast and good for alarms especially, but does super clean work all around...not a big shop but less overhead=better prices

 

Junior's Car Stereo in Fremont is pretty cool.