I'm trying to understand things here based on my CA experiences and knowledge. The Insurance company in question here is YOUR insurance company? As in they are the ones you have a policy with?

If so, they should Honor the car's current Retail Value on the market. You need to grab hold of a few ads for similar cars in the condition your car was in prior to the accident. Show at least 3 - 5 cars in the price range you are seeking.

Additional, before taking any money from them, ask them to provide you with your Policy's Maximum Limits of Liability on that car. Most Insurance companies will refuse and say you are not privy... hold your ground and tell them there will be no settlement till that is provided to you.