I own a 1997 Cavalier and am interested in upgrading the sound system. Since I'm new to car-audio brands and manufactures, I'm clueless on what determines high and low quality. I'd like to have more up-to-date features (AUX, USB) on a moderately priced head unit, and some input on speaker brand quality. All of the audio is stock. If I purchase a new head unit with some speakers will that substantially increase my sound quality? If not, what else should I do?