You asked for opinions. Here is mine. When buying a car of that age, you may as well throw any "book" values away. You apparently understand that. The $8000 is very high for that car BUT .... I have paid $1000 more than "usual" for a 123 (300D turbodiesel) and was glad I did. The difference between an average value and a high value in an older car is, in my opinion, service records. It sounds as though the $8000 car has plenty of record history and the others do not. Now $8000 is still too high I think. I would still pay a premium for that car but would offer $7000 and negotiate from there.

One more aspect though; If one is willing to pay a premium for a car it should have everything one wants. That means if you don't like the way the interior looks, don't buy it. I would hate to get in my "overpriced" car every morning and wish it had a black or burgundy (or whatever) interior. It sounds like you are not desperate for another car right now. There are plenty out there. Just look for service records.