Should I shop for better car insurance rates?

I am looking to buy a new car. It is a 2005 Pontiac Sunfire. I live in Wisconsin, am 29, and have an excellent driving record. I need full coverage, and called my insurance agent (Progressive- which I've been with for over 12 years) and they said, for an average, about $500 every 6 months. Is this a little high or is this about average. Are there any other car insurance companies that might offer better rates?