Hi Vito,
When you disagree with an insurer on the pay-out value your best bet is to demonstrate to them that similar or even identical cars are worth a lot more than what they are offering.
It seems as though you've already been able to find other CSL's for sale, I assume you've sent this in, what was the outcome of this first of all?
Feel free to ask away with any queries and I'll help as much as possible, I've been dealing with these idiot insurance companies for 10 years now!