I've come to the realization that every insurance company's rates are based on so many variables you can't predict who might be cheapest. That's how Progressive can say "people who switched from Geico saved $448", and Geico can say "people who switched from Progressive saved $329". You must shop around. Your quote will depend on many factors, down to the zip code, so a guy two blocks away could be quoted $150 more or less than you.
When we switched to Liberty Mutual we saved $300/year. Five years later, after painful renewal increases, we saved $600/year leaving Liberty Mutual just a few weeks ago.$600 is huge.
I was excited a few years back when I was able to get into USAA, only to find their insurance quotes were not competitive for us. Neither was Amica, Progressive or Geico. This time we used an independent broker who reps for 18 different companies, worked out great.
Don't restrict yourself to only getting quotes from places where you can do it online. Also got a great tip from the insurance broker - if we ever have a claim, call him first. He'll take the info then contact the insurer, to make sure I don't innocently say something that will screw up the claims process.