My insurance for an 07 S550 is around $800 a year and that is with $500,000/1,000,000 coverage. Not to bad in my mind. My wifes 03 Acura MDX costs around $600 for the same coverage. MPG for my S550 is better then the SUV I used to drive.
Just a pointer to you. There is a much cheaper way to insure yourself. If you have more than one vehicle it makes for great savings. Drop your coverage to $300k/$300k (this is the insurance world's standard rate to qualify for umbrella, but double check with your carrier) on both or all vehicles. Call up your insurance company and ask for umbrella coverage. You can get $1 Million worth of coverage for about $200 per YEAR and that coverage applies to ALL of your vehicles on your policy and it also covers your home (assuming you own it). Make sure to shop around. Generally insurance sold directly to consumers and not thought agents is much cheaper (no commission). If you are married, list your wife on the policy. Married men have a statistical lower accident/claim rate. You will save money (5-15%) simply by listing her.