I've got a good number of vehicles covered with Grundy (including the '08 Z4). Agreed value coverage, no mileage limit. The vehicle can't be your daily, and it must be garaged.
http://www.grundy.com/
A buddy's vehicle (insured with Grundy) sustained much damage when a front suspension failure sent him off the road. The adjuster was super knowledgeable...but while in for the repairs, additional damage was found. She came back for a look then covered the new found damage with no hoops to jump through. You couldn't help but be impressed...even the guys at the body shop were. I like them.