I work for an insurance agency and we sell mostly Mercury Insurance policies because they're really the cheapest I've seen. Downside to Mercury is that they're REALLY nitpicky on your information and want to know extraneous details (who you live with, what cars they drive, etc.), customer service sucks, and you gotta make sure that any mods you have are put on the policy if you want them covered. My 06 Si under my AAA policy is something like $2K/year while under Mercury it'd be about ~$1.4K/year for the same liability coverages.