Definitely Amoeba for the music. Not only is used music cheaper but they have some harder-to-find stuff there. Parking is pretty bad there and taxis ain't cheap, so consider taking MUNI (the bus system) out there. The 71 line takes awhile to get there, but it stops about block from the store. Forget what else goes by there.
Cheap electronics? Not really cheap, but there's always Best Buy. Just don't ask the people who work there to help you unless you know exactly what you want. They're told to push certain items over other ones to make a sale, and can't be trusted to know their stuff. If you actually wanted an Apple brand iPod, go to the Apple store downtown. It's huge and worth a walkthru just for kicks.
Hardcore music shop? I really don't know about that. I'd stick with the Amoeba recomendation, and if you wanted to venture across the Bay into Berkeley you could try Rasputin.
Man, you guys are making me miss home. Boo Roseville, where you need a car to get around, and everything is generic. At least they have a Chik-Fil-A here and a Sonic being built. Sigh.