Ten years in L.A. and I haven't yet walked into an audio store that I would go back to. Your best bet is with the appointment-only guys. Elliot at Acoustic Image is great, but of course only if you're looking to hear something specific. Jay at Audio Revelation is also super to deal with, but he's a 2 1/2 hour drive south of downtown L.A.
There are a few new Vinyl stores in the area, Vacation in the Los Feliz neighborhood and Origami in Echo Park, both close to downtown (I haven't made it to either yet). Poo-Bah in Pasadena is long-established and fun to visit. It's a few miles away from downtown.