I was at fault in an accident and am being sewed for difference after insurance settlement offer?

I was at fault for an accident. Both cars were totaled. I was offered a fair amount and have settled. However the other party was offered $3000 and feels the car is worth $4400 according to NADA. They found a comparable car for $4500 are asking for the difference between the $4500 and $3000 plus the sales tax on the $4500. They are sewing me in small claims court for the amount equaling about $2000. What do I do?