My stock radio has been making sizzling sounds when I change the volume/station. Also, one of the rear speakers doesn't work at all, and the other is very weak. Thinking this was the head unit, I ordered a cheap clarion off Crutchfield. But I just talked to a Crutchfield advisor via chat, and they said that if I wanted to install it, I would need a relay, oem adaptor, and a wire harness receiver, and that there is no possible way I could make the radio work without these things. In my old car (Mazda), I did not need anything...I just crimped the wires together and everything was fine. What's wrong here?