Crunching the figures

MY PARTNER was hit while waiting to turn right at traffic lights. The damage to our six-week-old Mazda 6 Sportwagon is considerable. The centre pillar, doors and sill need replacing, and the rear quarter panel, front guard and other panels need repair. The repairer suggested by my insurer estimates the cost at $6000. Another repairer says given the age of the vehicle and the structural work needed, it should become a repairable write-off because my policy will replace a car up to two years old. My concern is I know the car won't be repaired to my standards, and I know from experience that a car is never the same after repair. Where do I stand with the insurance company if I don't agree with the assessor's opinion? Can I ask that it be made a repairable write-off or are there other avenues I can take? I want a new car not for personal gain, but because of its age. I don't want a new car that has been cut up and welded together.