For selection and maybe service, Ambrosia is probably "the best." But, although Ive never bought anything from him, I have really enjoyed my visits with Randy at Optimal Enchantment ((310)393-4434). Especially if you are interested in analog, call him and make an appointment.
That's all there is on the west side of town. And, frankly. that's all there is in Los Angeles proper. GNP in Pasadena is pretty good. Upscale Audio way out there has good stuff.
Closer to the west side, in the South Bay, not a store but you can make an appointment to audition stuff at Reference Audio Video in Torrance. They have BAT, Sony sacd stuff, Proacs, lots more. And, again, to be frank, there is no one in this business more pleasant, honest and informative to deal with than Ken Ito, the proprietor of Reference. Call him at 310 517-1700.