I also recommend wired for sound...
However, did you try Soundsations in newhall? San Fernando rd and Market. I see boats or rv's every time I drive by there, and he has been in biz there a long time
i do hear they do good work but had a buddy of mine have a bad experience with them f'ing up his fenders on his trailer, not really a place i want to trust with my truck, seem a little careless..i dunno maybe i will check them out anyways.