Not LA area.. but worth the drive.... i take my stuff to Pacific Audio. They do magazine work and high end diesel performance (PPE). They've been in business for years and are not a fly by night type of place.
Anyways, they're not the cheapest and usually super busy.. but they great work on RV's, boats, custom setups and of course the SMB's.
http://www.pacific-audio.com/address.html
They just installed a head unit in out rig a few months ago and did a great job. It was a piece of cake for them.
I agree with not going to AL and ED's. The stereo we replaced was installed by those Yahoo's and the job was done so bad, i have Pacific clean it back up.